Nen

Nen (念, Mind Force) is one of the defining features of the manga Hunter × Hunter by Yoshihiro Togashi. It is a technique that allows a living being to use and manipulate their own life energy (known as aura). Because one can craft a great variety of para-psychological abilities through Nen, it is considered a dangerous power that is not known to the public at large. The term "Nen" can also be used in conversation to refer to aura. A person capable of utilizing Nen is colloquially referred to as a "Nen user".

Awakening and Use


Aura (オーラ, Ōra) is the life energy produced by all living bodies vital for survival. Aura from all parts of the body has a tendency to flow together, producing one mass of energy. This happens without the individual's awareness, typically resulting in a slow leak of aura continually escaping the body. If one were to lose their entire aura, it would be equivalent to using up all the energy keeping them alive, which would be fatal. The pores or points on the body from which aura flows out from are called "Aura Nodes" (精孔) (しょうこう, Shōkō). Controlling those nodes is the first step to being a user of Nen. Grave wounds such as mutilations can disrupt the flow of aura in the affected body part and even stop it altogether.

Aura looks similar to the water vapor from a kettle. It is possible to feel its presence without being aware of its existence. It has been described as feeling like a warm, viscous fluid at rest, whereas powerful, refined auras produce a sensation that feels akin to needles pricking into the skin. Hostile aura generates extremely unpleasant sensations, which can cause a non-user to halt in their tracks and be unable to walk towards the source as if a wall had been erected in front of them. Since every living being emits aura subconsciously, learning to sense aura is a useful skill for those tracking living things or hunting non-living things infused with aura. An experienced user of Nen can judge the location and relative strength of their opponents through reading the output of their aura.

Learning Nen and Initiation
A student learning Nen trains to manually open and close their aura nodes so that they can control the flow of their aura. One typically learns this process slowly and gradually through meditation. The second method (colloquially called Initiation or Baptism) is by having one receiving an influx of aura from an experienced user that forces these nodes to open. Despite being much quicker, this method is typically frowned upon by Nen instructors due to the danger it poses to the student if the user is inexperienced or has malicious intent, and it is not considered a standard teaching method. Initiation via physically attacking another with the use of an enhanced aura typically causes permanent disability, an injury, or death.



There is, however, a way to initiate that is less harmful to the student's body—depending on gently jolting open one's nodes forces the new user to learn to control their aura flow, else risk suffering severe exhaustion or death. This method is called Gehou. Once one has opened their aura nodes, they will be able to see their own aura as a shroud surrounding the body due to the nodes in their eyes being opened.

Nen of the Flame
Nen of the Flame (燃, Nen) is sometimes used in Shingen-ryū kung fu as a precursor to learning the actual Nen. They are mental exercises akin to meditation that strengthen one's force of will. Regular practice can smooth the flow of one's aura. The Four Exercises of Nen of the Flame are as follows:

Upon his introduction, Wing taught Killua and Gon the Nen of the Flame as a fake sense of Nen that focuses mostly on meditation and on one's self. Not all steps of this method directly manipulate aura and most have no visible effect; however, after Gon was injured by Gido and forbidden to use Nen for two months to recover by Wing, both Gon and Killua practiced this method, and in fact made it more natural for them to use regular Nen. Given that Nen is linked to emotions and mental state, this method can be particularly useful to train Nen without aura, although normal use of technique is usually preferred.
 * Ten (点, Point): Focus the mind, reflect upon the self and determine the goal.
 * Zetsu (舌, Tongue): Put it into words.
 * Ren (錬, Temper): Intensify your will.
 * Hatsu (発, Release): Put it to action.

Nen and the Hunter Association
Acquiring control over one's aura flow is the final step to becoming a professional Hunter, as per the second Hunter Bylaw. According to Wing, this is because Hunters need to be deterrents for crime. However, since Nen could be extremely disruptive to society, it was deemed unsafe to include it as a publicly-known criterion and an official part of the Hunter Exam, and is therefore known within the Hunter Association as the "secret Hunter exam". A licensed Hunter may not reveal the existence of Nen to those who do not know about it, although it is possible to relay this information in times of emergency.

Many Hunters are proficient Nen users, with Isaac Netero, the 12th Chairman of the Hunter Association, being revered as the world's most powerful Nen master in his prime. Accordingly, many high-profile contracted jobs list knowledge of Nen as a minimum requirement.

Geniuses


Nen is like any other skill, in that there are those who will learn it faster than others. Some are able to discover and learn to manipulate their aura on their own without having formally learned it. These individuals are typically known as "geniuses", "psychics", or "superhumans" to the public. This can be anything from inadvertently being able to use the basic techniques of Nen or unconsciously developing a unique Nen ability that can be used without really understanding how or why one is able to do so. Typically, geniuses of Nen are exceptional artisans in their own fields and their abilities are related as such.

Notable geniuses within the series include:
 * Neon Nostrade, the fortuneteller.
 * Benny Delon, the mass-murderer and blacksmith.
 * Zepile, the counterfeit artist.
 * Komugi, the Gungi world champion.

Nen and Emotion


Although the production of aura is unconscious and constant by all living beings, it is not only life energy. Aura carries with it the desires and emotions of the one who deploys it, which is what allows for Nen to have an incredible versatility to those who develop their skill at using it, and also heavily influenced by mental condition and emotional state. A basic application of this phenomenon is that one can channel their aggression or malice into their aura and deploy it towards another person (i.e. blood-lust). The antagonized will then be able to feel that blood-lust as if it were physically palpable; if unable to keep it from their own body by deploying their own Nen, he/she may be physically harmed by it.

Vows & Limitations


Being a product of the mind, Nen responds to the goals, strengths, and desires of individual users. As a result, a student of Nen can increase the overall power of an individual skill by stating a self-imposed restriction that forces even more conditions on it. For example, if one consciously decides something along the lines of "I will only use this skill on Thursdays" or "I will only use this skill against short people" and manages to abide by that rule, that particular skill will become stronger. These conditions are called "Limitations" (制約, Seiyaku), and the act of swearing to respect them "Vow" (誓約, Seiyaku) or "Contract". The stricter the Limitation, the more one's ability is strengthened. It is implied that Limitations that carry great meaning or are tied to emotional states also bring about a greater benefit. However, Limitations are also considered liabilities, since the power they grant is not consistent and breaking a Vow not only entails the loss of the ability it was used on, but it also carries the risk of obliterating one's capacity to use Nen altogether.

Limitations that contain some sort of punishment (e.g. "I will die if I break this rule") will strengthen the ability even further. An example is provided by Kurapika, who swore on his own life not to use an ability on anyone but the Phantom Troupe. According to Izunavi, without that added risk, the ability would not have worked.

The Unknown
Though Nen is influenced by one's mental condition and emotional state, it is difficult to judge exactly how these factors affect Nen. In certain instances, these factors may even lead to one exceeding the 100% limit cap. However, using one's powers beyond their capacity will ultimately cause strain. Potentially, this could become either a weakness or fatal to the user. Gon is an example of exceeding the 100% limit cap: after the boost, he would have died without Alluka's intervention, and even so, he reverted to a stage where he cannot use his aura. According to Ging, he was lucky to get away with only that, and if he wants more, there will be a price to pay. Nen also does not necessarily disappear following death. In fact, sometimes death can reinforce an ability's strength. If someone dies holding a deep grudge, their Nen will remain and seek out the object of hatred.

Four Major Principles


In order to fully grasp Nen, one must first learn the Four Major Principles of the Shingen-ryū school of kung fu. Everything else, including a practitioner of Nen's individual skills, is based on the basic manipulations of one's aura flow. The Four Major Principles, in order of study, are: Ten, Zetsu, Ren, and Hatsu.

These basic techniques become second-nature to those experienced in Nen. For example, a beginner must learn to use Ten and concentrate to maintain it; whereas someone with experience will practically always be in a state of Ten, even during sleep.

Ten


Once a person has opened their aura nodes, they must learn to keep their aura from leaking away from their body. Ten (纏, Envelop; Shroud) is the process of keeping the nodes open, but also having aura flow through and around the body rather than away from it. Once maintained, it creates a shroud around the user that feels similar to standing in lukewarm, viscous fluid. Ten maintains youthful vigor and reduces one's aging, since the energy powering the body no longer leaks away; one can keep the body from breaking down and deter the aging process. Ten is the most basic defense against emotional Nen attacks, and it also offers limited protection against physical attacks, but hardly any when said attacks are enhanced with aura. Through frequent meditation and practice, one can improve the quality of their Ten and even maintain it in their sleep. Once it has been learned, it will never be forgotten, much like cycling and swimming. Despite being the most elementary technique of all, Ten is also one of the most important, as the more polished it is, the more precise one's control over their aura.

Zetsu


While Ten allows a user to keep aura from leaking away from their body, Zetsu (絶, Suppress; Null) stops the flow of aura from their body altogether. By closing all of their aura nodes, the user is able to halt all outflow of their aura like water from a valve, making their presence much harder or even impossible to sense. Since the user is no longer surrounded by their own aura, they are more sensitive to the aura of others. The enhancement in perception is such that Zetsu can counter In, although it is not advised to employ it this way. This technique is thus doubly useful when tracking another person, as not only it will make it easier to follow them, it will also prevent other users of Nen from noticing their pursuer. However, there are other ways to perceive a person hiding with Zetsu: aside from the five senses being effective, particularly perceptive individuals are capable of detecting the gaze of another person, although they might not manage to discern the position and number of onlookers. Furthermore, if Zetsu is utilized within a certain range from a Nen user, that Nen user might notice their presence disappearing, especially if the Zetsu user's aura is powerful. Despite the technique not affecting vision directly, activating Zetsu in front of someone else will give them the impression the user has turned transparent.

Zetsu can also be used to relieve fatigue, since it forces the body's external layer of aura to be fully contained within. However, for the same reason it can be dangerous due to it leaving the body defenseless against any aura attack. Even a weak attack enhanced with Nen could do massive damage. Since even the thin protection offered by Ten is gone, a Zetsu user is particularly susceptible also to hostile emotional attacks, resulting in their mind becoming as vulnerable as their body.

Ren


Ren (練, Refine; Enhance) focuses on outputting a larger amount of aura than Ten, projecting it outwards explosively. This amplifies the user's physical strength and durability and provides a large pool of aura for any advanced techniques or individual skills they decide to use, albeit at the cost of expending said aura. One can train their Ren to extend its duration and increase the amount of aura at their disposal. It is said it takes one month to prolong one's Ren outside of combat by 10 minutes. If Ten is considered purely defensive, Ren can be regarded as its offensive counterpart, although it also grants the user vastly enhanced defensive abilities. With the right timing, Ten can be used to contain the aura produced with Ren.

By tingeing one's Ren with hostility, a Nen user can exert what is colloquially referred to as "blood lust". A prolonged emission of malicious Ren can induce uncontrollable dread in those who cannot use Nen, paralysis and, if contrasted without Ten, even death. On the other hand, a neutral Ren can rarely be felt by non-users. Since Ren is a show of power, it can also intimidate other Nen users, as it offers an approximate measure of the user's raw strength; in fact, by "show me your Ren", Hunters generally mean they want to see the fruits of one's training, such as a Hatsu ability, rather than their Ren per se. In most cases, Ren reflects the user's hostility without their control, and it can even leave faint traces in the environment after the Nen user has left the scene.

Hatsu
Hatsu (発, Release; Act) is one's personal expression of Nen. Its qualities are influenced by but not restricted to the Nen user's natural Nen category, one of the six available, which is decided by nature and nurture. Hatsu is used to project one's aura to carry out a certain function, creating a special and unique paranormal ability that is colloquially called "Nen ability", "Hatsu ability" or simply "Hatsu".

At first, Hatsu appears simply as a consequence of using Ren during Water Divination; however, it is more than a mere property of the latter, and it can trained on its own either through the Water Divination itself, which however seems to only affect the user's natural category, or a desired Nen category via specific exercises. Once it is sufficiently honed, the student can attempt to create their personal Nen ability. Since they can have an immensely vast range of effects, Hatsu abilities may be recognized as any manifestation of one's Nen that cannot be ascribed to one of the basic or advanced techniques, although there are instances of Nen abilities being essentially applications of Ko (an advanced Nen technique which however makes use of Hatsu) with special conditions or restrictions. A good Hatsu ability reflects a person's own character, regardless of its complexity; one can never truly master Nen if they only copy other people's abilities.

Advanced Techniques
After acquiring a working command of the basics, a student is introduced to a series of advanced techniques that often combine and/or derive from the our Major Principles. These techniques expand the user's options in combat manifold, but they also consume more aura than the Four Major Principles.

Gyo


Gyo (凝, Focus) is an advanced application of Ren by which a Nen user concentrates a larger than normal portion of their aura into one specific body part. It increases the strength of that one body part, but leaves the rest of the body more vulnerable. Gyo is most often used in the eyes, allowing a Nen user to see aura and Nen constructs concealed with In as well as faint traces of residual aura that might go unnoticed otherwise.

An alternative version of this technique gathers only the aura naturally leaking from the body instead of the greater amount produced with Ren. This application of Gyo can still increase the amount of aura in one select body part and thus its power, but the output is much lower than what is obtained through the regular technique. It is unknown if this lower-consumption Gyo could counter In. Given the circumstances of its usage, it seems Ten-based Gyo is an unofficial, intermediary step leading up to real, Ren-based Gyo (or Ko).

In


In (隱, Conceal) is an advanced form of Zetsu used to render one's aura imperceptible, effectively concealing it. Unlike Zetsu, however, In does not stop the user's aura flow; instead, it hides it, making it impossible to perceive with any of the five senses or extrasensorial perception. Hence, this technique is perfect for launching sneak attacks or laying traps, as it can conceal not only the user's presence, but also Nen constructs generated with Emission, Transmutation, or Conjuration.

In can be countered by using Gyo in the eyes or through Zetsu. Since In conceals all of the user's aura at once, experienced Nen users can divine their opponent is using it if no aura can be felt from them in circumstances which would normally equire it, such as during combat.

En


En (圓, Circle) is an advanced application of Ten and Ren. In Ren, aura usually envelops only a small amount of space around the user's body. En is when one extends their Ren so that their aura extends further than normal, then uses Ten at the same time to contain and give shape to that aura, normally a sphere. The minimum requirement is to extend one's aura to a radius of more than 2 meters and hold it longer than a minute. Someone using En can feel the shape and movement of anything entering the perimeter of their aura, with the degree of awareness and finesse depending on their skills. The downside to this technique is that it is extremely tiring and draining for the Nen user to constantly deploy so much aura. Those who master En are typically able to extend their En to a circle of a 50m radius. There are exceptions, however: Zeno Zoldyck, one of the most powerful assassins alive, is able to extend his En up to a radius of 300m. The Chimera Ant Neferpitou, has an irregularly shaped En and can extend a tendril up to 2 miles.

Shu


Shu (周, Enfold) is an advanced application of Ten. Shu allows a user of Nen to extend their aura's envelopment onto an object, allowing them to use that object as an extension of their own body. For example, one could use Shu to extend their Ten around a weapon, which would strengthen and protect it. Shu can be combined with other techniques, such as Ko.

Ko


Ko (硬, Temper) is an advanced version of Gyo in which all of the user's aura is concentrated into one particular body part. It is a combination of Ten, Zetsu, Hatsu, Ren, and Gyo. Gyo is utilized to focus aura on a part of the body, while Ten is used to prevent it from dispersing. With Ren, the amount of aura is increased even further. Zetsu is used to completely stop the flow of Nen in all other parts of the body. This makes that one body part extremely powerful, but at the cost of leaving the rest of the user's body completely unprotected. Due to the risk it carries, Ko is regarded as a purely offensive technique. An incomplete version of this technique can be utilized without Ren, primarily to master the other steps before increasing the amount of aura to concentrate and contain. Ko results in one's aura creating a high-pitched dissonance, somewhat akin to a tuning fork being struck.

Some Nen users, Enhancers in particular, employ Ko as a Hatsu ability by adding conditions to it.

Ken


Ken (堅, Fortify) is the advanced version of the basic Ren and Ten techniques. It is a primarily defensive technique where a Nen user maintains a state of Ren for a prolonged amount of time. The amount of aura surrounding the user's body during Ken is about 10 times higher than during Ten. Ken allows a Nen user to guard against attacks from any direction, but the large amount of aura produced makes it tiring to maintain. It is considered the best option to defend from Ko, despite not being as powerful as the latter on any given part of the body, as it protects all of it evenly. When not immediately at risk of being struck with Ko, Ken is utilized when one wants to be cautious. Some Nen users choose to expand its radius so as to sense incoming attacks they are unable to see, as a miniature En of sorts. Sometimes Ken is colloquially called Ren owing to the similarities between the two techniques.

Ryu


Ryu (流, Flow) is the term for use of Gyo from a state of Ken to perform real-time offensive and defensive value adjustments. If Ko devolves 100% of one's aura to offense or, much more rarely, to defense, and Ken splits it evenly between the two, Ryu is redistributing one's aura according to any other percentage, for example by focusing 70% of one's aura in one fist as one is about to strike, or 80% in one's leg to block an incoming kick. It is utilized to damage a Ken user without leaving oneself as unprotected as during Ko, although the power of the technique is lower. Ryu is a difficult technique to master, as it requires not only to control one's aura flow with great precision, but also to be able to estimate the amount of aura utilized by the opponent. Even if performed correctly, the movements of the aura flow risk giving away the user's next move.

Nen and Individuality
There are six types of aura; every individual is born having one of these six different aura types. Upon learning one's own aura type, a student of Nen can set about learning to apply the technique in a unique way that suits their personality, which can develop into a unique skill.



There are numerical approximations to indicate just exactly how efficient one would be at using aura abilities that one is not born into. Starting at one's own aura type, one has the potential to be 100% efficient at using abilities based in that category alone. Then looking at the category chart (see right), one has the potential to be 80% efficient at using aura types adjacent to one's primary type, 40% efficient at the opposite or farthest category, and 60% efficient in the two remaining categories. Specialization is typically unusable for non-Specialists because it is impossible to partially use; one either can or cannot use Specialist abilities. However, Conjurers and Manipulators have 1% potential of becoming Specialists due to being adjacent to it.

Water Divination


The most popular way (and the only sure-fire way seen in the series) of determining one's aura type is through Water Divination (水見式, Mizumishiki). Divination requires one to float a leaf atop a glass of water. A student of Nen will place their hands around the glass and perform Ren. The resulting effect from one's aura contacting the glass will determine a person's aura type.


 * If the volume of the water changes, the user is an Enhancer.
 * If the taste of the water changes, the user is a Transmuter.
 * If impurities appear in the water, the user is a Conjurer.
 * If the color of the water changes, the user is an Emitter.
 * If the leaf moves on the water's surface, the user is a Manipulator.
 * If a completely different change appears, the user is a Specialist.

It is best to base a Nen ability on one's individual aura type. Though it is possible for one to develop abilities outside of his primary aura type, one is typically less proficient at using those abilities. By creating an ability that one isn't suited for, one risks stagnating their potential by overloading their capacity for using Nen something Hisoka calls "Memory Overload". However, there are examples of Nen masters, such as Biscuit Krueger and Isaac Netero, who have reached a high level in multiple categories and employ them consistently in their primary Hatsu abilities. In fact, according to Biscuit, training in all the accessible categories is the fastest and most efficient way to improve one's skills in one's own Nen type, with the additional benefit of increasing one's flexibility and proficiency in Nen in general. A bell curve is the ideal shape, with the time spent on each category decreasing the farther away said type is from the user's natural one.

Hisoka's Personality Test
Hisoka claims that he is able to judge a person's Nen type based on their personality. According to him, all people of one aura type are generally of the same personality type. However, he also states that this method is similar to trying to find someone's star signs or blood type just from personality analysis—it is not always correct. According to his theory:


 * Enhancers are determined and simple. Most of them never lie, hide nothing, and are very straightforward in their actions or in their thinking. Their words and actions are often dominated by their feelings. They are generally very selfish and focused on their goals. This is reflected in their Nen as enhancers typically rely on simple and uncomplicated Hatsu techniques.
 * Transmuters are whimsical and prone to deceit. Transmutation users have unique attitudes, and many are regarded as weirdos or tricksters. Often they put forth a facade while hiding the truer aspects of their personalities. Even when they don't hide their personalities they rarely reveal their true intentions.  Many Transmuters rely on techniques that give unique and unpredictable properties to their Nen that reflects their personalities.
 * Emitters are impatient, not detail-oriented, and quick to react in a volatile manner. Many of them are quick-tempered and hot-blooded. They resemble the Enhancers in building their impulsivity, but the difference with them, they probably tend to calm down and forget easier. Because of the nature of Emission, many Hatsu techniques created by emitters are primarily long range.
 * Conjurers are typically high-strung or overly serious and stoic. They are often on guard as to be cautious. They are very observant and logical, rarely falling into traps. Being able to analyze things calmly is the strength of Conjurers. Many of the items that conjurers create are often used by them in a very deliberate and practical, logical fashion.
 * Manipulators are logical people who advance at their own pace. They are all for arguments and tend to want to keep their families and loved ones safe. On the other hand, when it comes to pursuing their own goals, they do not listen to what others might have to say about it. While manipulators often use techniques that allow them to control their opponents they also prefer to use an inanimate medium to control that can be used versatility (such as smoke or pieces of paper hardened with Shu).
 * Specialists are individualistic and charismatic. They won't tell you anything important on them, and refrain from being close friends, but, because of their natural charisma that draws others, they are always surrounded by many people. Because Specialization is unique and can have many facets, most Specialists possess only one Hatsu technique.

Telltale Signs
Furykov was able to construct a system to identify Nen users and their Nen types through observation alone, which he claimed is the result of his experience. According to him, a way to differentiate between Nen users and non-users is that the outline of the former's iris, when looked at from the side, appears discontinuous.

A person's Nen category can be determined through some habits of theirs and the flow of their Ten:


 * Enhancers and Transmuters, depending on their level of skill, have a soft, quiet Ten that shrouds the part of their body that activates their favorite attacks.
 * Emitters and Manipulators generally have a broader Ten, and if they attempt to shrink it, their aura will appear darker. Manipulators also tend to want to keep their dominant hand free, as it is generally the one used for their abilities.
 * Conjurers have strong aura around the part that activates their favorite abilities, and a much gentler flow everywhere else. Like Manipulators, they will also prefer to keep their dominant hand free.

Enhancement


If a student increases the quantity of water in the glass during their water divination, they are an Enhancer (強化系, Kyōkakei). Enhancement is the ability to use aura to increase the natural abilities of an object or one's own body. Therefore, Enhancers are able to greatly increase their physical attack and defense and are best suited for close-ranged melee combat. Affinity for this category plays a crucial role in combat at all times, even when Hatsu is not being used.

Enhancement is the most balanced category, allowing users to spread themselves evenly between offense and defense and become very powerful using only simple abilities. One of the examples of more complex Enhancement abilities include enhancing one's healing factor. However, it is a common belief that Enhancers generally do not need special techniques as their natural category already has the best balance between attack and defense as its primary attribute. This might play into why most Enhancement Hatsu abilities in the series appear to be mere applications of basic and/or advanced Nen techniques at first glance due to the lack of requirement to manage between pros and cons on an overall scale during their development.

Notable Enhancers include:
 * Gon Freecss
 * Isaac Netero
 * Wing
 * Gido
 * Dalzollene
 * Nobunaga Hazama
 * Uvogin
 * Phinks
 * Tsezguerra
 * Palm Siberia
 * Rammot
 * Menthuthuyoupi

Transmutation


If a student changes the taste of the water in the glass during their water divination, they are a Transmuter (変化系, Henkakei). An affinity for Transmutation means a person can change the properties of their aura to mimic something else, or only specific attributes. Altering the shape of one's aura falls in this Nen category too. Similar to Emission, constructs created via Transmutation are pure aura, therefore they are invisible to individuals incapable of using Nen. Transmutation is often mistaken for Conjuration due to their similarities. The difference is that Transmutation allows the user to mimic the properties of a substance with their aura, whereas Conjuration changes aura into the actual substance.

Transmuters are not limited to copying the properties of solid matter. For example, Killua Zoldyck uses his aura to copy the properties of electricity. Transmuters can also give their aura certain properties instead of replicating the characteristics of a substance in their entirety: Hisoka's Bungee Gum mimics and combines the properties of rubber and gum, and it is several times more flexible, sticky and durable than the real thing.

Notable Transmuters include:
 * Hisoka Morow
 * Killua Zoldyck
 * Silva Zoldyck
 * Zeno Zoldyck
 * Sadaso
 * Machi
 * Feitan
 * Biscuit Krueger

Emission


If a student changes the color of the water in the glass during their water divination, they are an Emitter (放出系, Hōshutsukei). An affinity for Emission means that a user has an easier time separating their aura from their body. Aura usually decreases in intensity very quickly when it leaves the source body, but adept Emitters can separate their aura from their body for long periods of time, over long distances, and still be able to maintain it and its functions. Emission is also required to manifest the effects of certain abilities away from the user, and to preserve those of Transmutation and Enhancement abilities after the construct or medium is separated from the user's body. Emission might also be involved in teleportation and in rendering one's aura able to phase through matter. Emitted aura appears to cap the user's output. In some cases, users have shown the ability to recover emitted aura; thus far, this has only occurred when Manipulation was also involved.

Due to its properties, Emission is typically employed in abilities with emphasis on range and/or those that have a long-lasting effects. Basic applications include shooting out projectiles or beams of aura at high speed. While this method is primarily used to attack, it can also be used to propel oneself. More skilled Nen users can combine this category with Manipulation in order to create Nen beasts. Some Emission abilities (such as Shachmono Tocino's, Razor's and Goreinu's) are commonly mistaken for Conjuration abilities. The two, however, are fundamentally different, as constructs generated by Emitters are created solely from aura, and are invisible to those who have not learned Nen.

Notable Emitters include:
 * Leorio Paradinight
 * Pokkle
 * Riehlvelt
 * Izunavi
 * Melody
 * Shachmono Tocino
 * Franklin
 * Razor
 * Bloster
 * Knuckle Bine

Conjuration


If a student creates an object in the water in the glass during their water divination, they are a Conjurer (具現化系, Gugenkakei). Conjuration is the ability to create a physical, independent, material object out of one's aura. Once a person has mastered the conjuration of a certain object, they can conjure it and dispel it in an instant, whenever they want. However, even if one were to completely master this Nen type, there would still be objects they could not materialize, such as swords that can cut anything, as they go beyond "human capacity". Izunavi vaguely described it as the inability to conjure objects overly supernatural.

Conjured objects can in fact possess special abilities. For instance, the Phantom Troupe bandit, Shizuku, is able to conjure a vacuum cleaner that can infinitely suck up objects, but with the condition that it cannot suck up living things and things made out of Nen. Similar to Manipulation, Conjuration abilities tend to be very specific, complex, and conditional. Conditions can be imbued into conjured objects to make them stronger. Kortopi, for example, is able to materialize a perfect inanimate copy of any object or person that he touches. However, the copies of all objects generated will automatically disappear after 24 hours. By resorting to Limitations, a Conjurer can take their ability a step further and materialize objects with properties that come even closer to exceeding human capacity, although they still cannot surpass it.

Conjuration is the only way in which Nen can create things that ordinary people (unaware of Nen) can see and touch, unless they are hidden from the senses with In. Furthermore, objects or entities created by this technique have a subtle "independence" to them. This means that they can continue existing even if they were at a considerable distance from the Conjurer, or even if the Conjurer themselves are not aware that they have yet to be de-materialized. Some Conjurers have also exhibited the capacity to alter the length and size of a materialized item.

Notable Conjurers include:
 * Kite
 * Kurapika
 * Basho
 * Shizuku
 * Kortopi
 * Bonolenov
 * Abengane
 * Genthru
 * Cheetu
 * Knov
 * Welfin

Manipulation


If a student moves the leaf floating on the water in the glass during their water divination, they are a Manipulator (操作系, Sōsakei). Abilities belonging to Manipulators allow the user to control living or non-living things in a certain way (and manipulate the aura itself), the main advantage being the ability to 'manipulate' enemies. Abilities of the latter type are especially feared, since the fight can be brought to an end as soon as the conditions are met. The degree of control is, for the most part, principally determined by a condition that may or may not put the Manipulator at a risk or a disadvantage (such as attaching objects on the enemy, touching the enemy in a certain way). Of course the higher the difficulty for the condition to be achieved, the better the degree of control. However, it is impossible to control a target that is already under the effect of Manipulation Nen.

Manipulators are the Nen users who can pour the most aura into an object. In many cases they are seen capable of inflicting and maintaining the effects of their abilities from afar, seemingly without the aid of Emission-type Nen. It can be reasoned that as long as the Manipulators are performing their abilities through a specific and consistent medium (such as Illumi's needles and Shalnark's antennas), with perhaps the inclusion of conditions, such result can be achieved. The medium used for Manipulation abilities must be something that the user has been in possession of for years, otherwise it will not be as effective.

Notable Manipulators include:
 * Illumi Zoldyck
 * Kalluto Zoldyck
 * Zushi
 * Squala
 * Baise
 * Shalnark
 * Morel Mackernasey
 * Shoot McMahon
 * Ikalgo
 * Shaiapouf

Specialization


If a student causes some other effect during their water divination, they are a Specialist (特質系, Tokushitsukei). It is possible that the effect that occurs can give some insight into how they should direct their ability. Specialization is anything that doesn't belong into the other five categories. This is the vaguest Hatsu category. For example, Kurapika's Specialist ability allows him to use all Hatsu types at 100% efficiency (for a Conjurer). Chrollo Lucilfer's Specialist ability allows him to steal any other Nen ability (provided that the right conditions have been fulfilled). Neon Nostrade's Specialist ability allows her to accurately predict someone's future in the form of a poem after the initiation conditions are fulfilled. It is possible to become a Specialist later in life, although it is more likely for Manipulators or Conjurers, which is why this category is placed at the bottom of the Nen chart. Since its position is dictated by a factor other than the affinity for other Nen types, it is currently unclear if it has the same acquisition rates as other categories, although it should be noted the presence of Specialization in the chart affects other Nen types regularly.

Of the many possible effects that can occur during a Specialist's water divination, only one was shown so far. Neferpitou's aura caused the leaf on top of the water to dry out and crumble.

Notable Specialists include:
 * Kurapika (Only when his eyes turn scarlet)
 * Neon Nostrade
 * Chrollo Lucilfer
 * Meruem
 * Pakunoda
 * Leol
 * Neferpitou
 * Meleoron
 * Binolt

Subcategories of Hatsu Abilities
Regardless of their type, some Hatsu abilities share common traits that allow them to be grouped in recognizable subcategories.

Clone
A clone (分身, bunshin) is a conjured copy of the user which is then controlled via Manipulation. Automatic clones do not require the user's focus, but they cannot carry out complex orders; vice versa, clones which are directly controlled by the user allow for greater precision, albeit at the cost of stricter conditions.

Notable clone users include: Kastro's Double may also be considered a clone.
 * Hanzo
 * An unknown assassin

Curse
A curse (呪い, noroi) is an application of Nen that is detrimental to the one upon whom it has been placed. Such curses are considered dangerous due to their long-lasting effects. The death of the caster may end up strengthening the curse, instead of weakening it. Curses may disappear if certain conditions are met by the cursed, but they can also be removed through the use of Nen.

Notable curse casters include: Abilities with similar effects to Judgment Chain are Genthru's Countdown and Knuckle's Hakoware, and like the former they can be lifted only by an Exorcist.
 * Kurapika

Exorcism


Those who possess the ability to lift curses are called Exorcists (除念師, jonenshi), but are rare among Nen users. The Hunter Association may have only one among its members. There are fewer than 10 people in the entire world whom are powerful enough to exorcise Nen curses left by the dead.

Notable Exorcists include: Nanika can perform exorcism through wish granting.
 * Abengane, the shaman.
 * Hina
 * Unknown exorcist in the Hunter Association.

Nen Beast
A Nen beast (念獣, Nen-jū) is an artifact made out of aura endowed with some degree of agency. Its abilities and degree of autonomy vary greatly depending on the Hatsu ability that created it and the user's skill. Nen beasts generally have anthropomorphic or animal appearances, but that is not always the case. The only time the term has been referred to an ability with a confirmed Nen type, the Nen beasts in question were generated with Emission and controlled with Manipulation. It was later used to refer to Nen constructs which were visible to Nen users without the aid of Gyo (suggesting they were not hidden with In), but invisible to all others, which suggests they were expected to have similar properties. However, it remains unconfirmed whether only proxies that fall in those two categories are classified as Nen beasts.

Notable users of Nen beasts include: Razor, Knuckle Bine, and Musse may also make use of Nen beasts.
 * Goreinu
 * Nasubi Hui Guo Rou
 * The 14 Princes of Kakin

Parasitic Type
See also: Guardian Spirit Beast

When a Nen user bestows a Hatsu ability onto another person, that ability is said to be of the parasitic type (寄生型, kisei-gata). Parasitic type abilities are similar to curses and are often conjured. They utilize the host's aura to invoke their abilities. Many of them are conjuration based but they can come in other forms as well. They act without the host's awareness or control, defending him/her and, in rare cases, attacking. The person who receives the ability may not even be aware of it or be a Nen user, in which case they will be unable to see the ability. The latter case is the most favorable for parasitic Nen, as the host will be unaware of their aura being drained and will only feel tired. Many abilities of this type feed off the emotions of the recipient as well as of those of the people around them, resulting in complex, unpredictable Nen constructs.

Notable users of parasitic Nen include:
 * The First King of Kakin who created the Seed Urn.

Notable hosts of parasitic Nen include:
 * Nasubi Hui Guo Rou
 * The 14 Princes of Kakin

Symbiotic Type
Some abilities are collaborative in that they require multiple Nen users to donate aura or perform each a different task to be effective. The power of the resulting ability is greater than what the Nen users involved could achieve individually. Such abilities are classified as symbiotic type or joint type (相互協力型, (ジョイントタイプ) ). An example of symbiotic ability is conjuring a weapon which is then loaded and fired by another Nen user, such as an Emitter.

Notable joint type Nen users include: Tsubone may utilize this type of sub-ability as well. The Ortho Siblings' ability shares some similarities with joint-type abilities in that it requires two Nen users, despite being different overall from any previous one.
 * Golem
 * Kurton

Enhancement and Limitations
Reinforcement Nen plays a crucial part in combat, and as such, one's affinity for said Nen category is a factor of paramount importance. For example, while a skilled Conjurer may be unable to fully block 9mm bullets with Gyo, some master Enhancers can utilize Ten or Ren to resist sniper bullets without a single scratch, as well as to come out of the head-on explosion caused by an anti-tank bazooka with only minor burns. When two Nen users clash, it is possible to make predictions about the outcome through a simple equation. Physical strength is represented by the acronyms AP (Attack Points) and DP (Defense Points), depending on the action of the Nen user, while the proficiency in Enhancement is expressed in SP (Spirit Points). The sum of these two factors indicates the value of one's offensive or defensive capabilities.

If an Enhancer and a Conjurer who possess equal physical strength and who have maximized Reinforcement were to clash, and the Enhancer was the one attacking, his attack power would be expressed as:

AP + SP → 100 + 100 = 200

For the Conjurer, who has the same physical strength but whose proficiency in Enhancement would not exceed 60% even if maximized, his defense power would be:

DP + SP → 100 + 60 = 160

The equation representing the action is:

(DP + SP) - (AP + SP) → (100 + 60) - (100 + 100) = -40

Thus the Conjurer would suffer 40% of the damage even if he managed to block the attack correctly. This method is a simplification, since physical strength and aura output differ from person to person, and the location, environment and moment of the attack are fundamental variables in a real fight. Nen itself is much more complicated, since its power varies depending on the user's mental state. Because of this, it is possible to use a Limitation to strengthen one's will and thus one's aura, exceeding the normal limit. If in the same instance as before the Conjurer used a Limitation worth 2 MP (Mystery Points), his defense would become:

DP + SP x MP → 100 + (60 x 2) = 220

As a consequence, the equation would be:

(DP + SP x MP) - (AP + SP) → [100 + (60 x 2)] - (100 + 100) = 20

In this case, the Conjurer would be able to block the Enhancer's attack without suffering any damage. However, due to the inherent risks of a Limitation and exceeding one's 100% limit, not all Nen users decide to resort to this method.

Level, Force, and Accuracy
A Nen user's "Level" in a Hatsu type determines the abilities that Nen user can learn. It could be tentatively defined as degree of proficiency in a Nen type which translates in the creation of a specific ability. A Level 10 Conjurer can only master Conjuration abilities that require an amount of skill equal to or lower than Level 10. The Level of one's natural category determines the ceiling for all others, which can be calculated by applying the rule of affinity: a Level 10 Conjurer can master Transmutation abilities only up to Level 8, Enhancement and Manipulation abilities up to Level 6, and Emission abilities up to Level 4, unless he raises his Level in Conjuration by training in it  (or by training other types, which would cause his skills, and thus his Level, in Conjuration to increase as well).

However, while said Conjurer could potentially create the same ability as a Level 4 Emitter, his effective output would pale in comparison with the Emitter's. The reason is that the law of acquisition rates applies a second time, making it so the "Accuracy" and "Force" (which have also been translated collectively as "Effectiveness" or "Power") of a Hatsu ability are proportional to the predisposition of the user for the category the Nen ability requires. As a consequence, if the Level 10 Conjurer and Level 4 Emitter from the example used the same Level 4 Emission ability, the Force and Accuracy of the Conjurer would amount to a measly 40% of the Emitter's, who has 100% affinity, and thus 100% Force and Accuracy, for that type.

Aura Power
Knuckle Bine devised a way to convert aura in a numeric value, and use it in a system similar to the process of finding the Capacity factor of a power plant, in this case the power plant being the Nen user and the energy being the aura. The arbitrary unit of his system corresponds to the approximate amount of aura spent every second by a Nen user in battle mode (1 unit per second), and it is called "aura". However, once the fight starts, the aura consumption increases up to 6 or even 10 aura per second, due to the usage of techniques like Ryu and Ken and of Hatsu abilities. The less skilled the Nen user and the more powerful the technique, the more aura is consumed this way. Inexperienced users can consume as many as 10 aura per seconds with Ren, with the annexed increase when they utilize advanced techniques. After assessing how much aura his opponents spend in combat every second and for how long they can keep using it, Knuckle is able to estimate the total amount of aura they can access. He uses three parameters:




 * Maximum Aura Power or M.A.P. (最大オーラ量 or MOP): the amount of aura stored inside the body of a Nen user. It varies for each individual and can be increased through training.
 * Potential Aura Power or P.A.P. (潜在オーラ量 or POP): the amount of aura that a Nen user can expend before passing out. It appears to correspond to how much of their M.A.P. a Nen user can access at a specific point in time.




 * Actual Aura Power or A.A.P. (顕在オーラ量 or AOP): the quantity of aura that is used effectively at any moment; in other words, aura output. This is what determines the efficiency of the Nen user in a combat situation, as a high P.A.P. with a low A.A.P. is meaningless. A.A.P. can be increased through training. It is also influenced by how well an individual can use Nen: lack of practice or low affinity for a certain Nen category can cause the power of an attack to be lower than the aura units expended. For example, when Gon used his Round 2 technique against Knuckle, he consumed 4000 aura to charge two abilities, Rock and Paper; however, the actual force of the Emission attack was equivalent only to 500 aura, 25% of the power of Rock and 12.5% of the aura consumed overall.

Training Exercises
Orthodox Nen training begins with meditation exercises, which are aimed at allowing the student to gradually become aware of their aura flow even before their aura nodes are opened and to start to control it. In Shingen-ryū kung fu, meditation (the Ten step in the Nen of the Flame) is also utilized as a way for the student to polish their mind and thus the flow of their Ten.

The first exercise has the purpose of ascertaining the student's natural potential. They are required to put his index fingers slightly apart, and have the tips close in on each other until they have the sensation of pushing against something. The farther apart the fingertips are when the student begins to feel the presence of aura, the greater their predisposition.\ Queen Oito and Prince Tserriednich performed this exercise at their instructor's request, Bill and Theta respectively.

What follows is the basis of aura manipulation, even if the student is still incapable of seeing aura. In the first and only known exercise of this phase, the student to place their hands in front of their chest and imagine forming a ball between them. This exercise is meant to develop the student's ability to feel their own aura. In general, it is performed for 10 days, with 3 sets of 10 minutes every day.

Once all of a student's nodes are opened, they are introduced to the first technique, Ten, followed by Ren, which in turn leads to Gyo and other techniques. When Hatsu is introduced, it is first trained through the Water Divination exercise, by having the student attempt to produce a more pronounced change. Mastering Ten in six months is indicative of uncommon talent. Regardless of the student's level, it is advised they train their Ten and Ren daily, since they are the foundations of all advanced techniques.

Biscuit's Training
Biscuit has devised exercises to train her students in every aspect of Nen after they master the basic techniques enough to pass the secret Hunter Exam. She models her coaching method on her students to best suit their needs, often giving them very precise instructions but also letting them reach the answer on their own from time to time. Unlike her former pupil Wing, she has her students train their guard and physical, combat and analytical abilities together with Nen. By her own admission, her regimen is much harder than his.

Gyo Training
The first exercise she has her students perform requires them to rapidly activate Gyo on their eyes and tell her what number she is forming with her In-concealed aura whenever she raises her index finger. Should she have more than one student, she makes them compete amongst each other, and the slower one to reply is penalized with physical exercises. Should all her students be too slow, all of them will be punished. There is no set time for this exercise, and in fact it is used to teach students to remain constantly vigilant and activate Gyo at the slightest hint of danger, until it becomes second nature to them.

Shu Training
On Greed Island, Biscuit had Gon and Killua dig through rock formations using regular shovels, confiding that they'd be able to figure out the existence of the technique and how to utilize it all on their own.

Ken Training
After explaining how to perform Ken, Biscuit proceeds to demonstrate Ko and demands that her students maintain Ken for at least thirty minutes, during which she holds Ko as if about to strike. Once they manage to hold the technique for that long, she hits them with a slow-moving Ko punch to test their resistance.

Ryu Training
When a student manages to hold Ken for at least 30 minutes, they are ready to learn Ryu. Biscuit instructs them on which proportions of their aura to focus on which body part for 30 minutes, three times a day. At the same time, her student are introduced to the kumite section of her program, in which they spar using Ryu, so as to learn how to adjust their aura flow while attacking and defending.

Ko Training
Biscuit's exercises or Ko training were not shown, but it appears the technique is taught at some point after the Ken exercises and before the Hatsu ones, as the first of the latter requires the use of Ko.

Hatsu Training
See also: Biscuit's Hatsu Training

These exercises are structured in levels, and the student can generally progress to the next after achieving a certain degree of mastery over a lower one. Her students train in all accessible Nen types, as, on top of granting them more flexibility, this allows them to progress in their own category more quickly. Her fundamental rule is that only one Nen category can be trained a day. Students normally focus on their natural category every other day, while in the other Nen types are rotated and more are added as the student progresses. When coaching Gon and Killua, Biscuit introduced them to Enhancement first, and seemingly saved Manipulation for last.

Enhancement Training The student enhances a stone's durability using Shu and Ko to repeatedly smash other rocks without breaking the one they are holding. The exercise terminates either when a student manages to break 1000 rocks in a day, in which case they are ready for the next level, or when the stone they are holding shatters. On top of the aura consumption, the repetitive movement puts stress on the student's focus, causing their aura control to become less and less precise. Only one try a day is allowed.
 * Level 1 - Rock Breaking

Transmutation Training The student must form the numbers 0 through 9 on top of their finger by manipulating the shape of their aura, much like Biscuit does to train their Gyo, while also running. The student can proceed to the next level once they manage to form the 10 numbers in one minute, with the end goal being 5 seconds.
 * Level 1 - Shapeshifting

Emission Training This exercise is comprised of two parts. In the first, the student must form a small bubble out of their aura from the tip of their finger and maintain it in place for one minute. Once they manage to do so, they have to attempt to throw it over a certain distance without the bubble dissipating. The time the aura bubble can be maintained afloat reflects the strength of one's Ten. Effort is also required to maintain the shape of the bubble.
 * Level 1 - Name Unknown

The student positions into a one arm handstand, then they project their aura outwards explosively from the hand that is touching the ground so as to propel themselves into the air. The student can proceed to the next level once they manage to launch themselves a few dozen centimeters; otherwise, they keep practicing for as long as they can maintain the handstand. A student who has mastered this level is able to knock an opponent back a dozen feet with an Emission attack.
 * Level 5 - Floating Hand

Ren Training
Very similar to the basics of Ken training, this step of Biscuit's regimen is intended to increase the student's aura pool, in particular to allow them to maintain Ken for longer in combat. In order to accelerate progress, she can speed up the student's recovery with her Hatsu ability. Once the student manages to maintain Ren for three hours, they will still have to hold it for that amount of time once a day. Biscuit also had Gon and Killua fight Knuckle right after the end of the exercise.

Trivia

 * In the manga, five characters have used Nen before it was explained to Gon and Killua: Illumi (Hunter Exam arc), Zebro (Zoldyck Family arc), Hisoka, Zushi, and Wing (Heaven's Arena arc).
 * Aura can be filmed, but it will still remain invisible to those who cannot use Nen.
 * The terms used for "Vows" and "Limitations" are homophones in Japanese (せいやく, Seiyaku).
 * Kurapika is the only character who falls under two different Nen categories.
 * Manipulation is the only category of Nen that none of the protagonists fall under.
 * Aura is translated as "Chi" (氣) in the Chinese edition of H × H. Chi is known as "Ki" (気) in Japanese.
 * In the 2011 anime, the equation representing the power of Limitations is different from its counterpart in the manga, with Mystery Points affecting both Attack Points and Spirit Points:

(AP + SP) x MP = ?


 * In Japanese, the acronyms MAP, PAP and AAP were written as MOP, POP and AOP due to the katakana transcription of "Aura", which is "オーラ", or, in rōmaji, "Ōra". To preserve the original acronym, Viz excluded "aura" from them in the translation, with the "O" standing for "Output".
 * Furthermore, the "P" in all three acronyms stands for "Power", but the kanji "量" actually means "volume".
 * Despite Izunavi stating the position of Specialization in the Nen chart is due to the fact that Conjurers and Manipulators have a 1% chance of becoming Specialists later in life, it has been shown multiple times that the presence of this Nen type affects all others: for example, Conjurers have 60% affinity for Manipulation instead of 80% because Specialization is located between the two in the chart.
 * While using Ken, Gon's aura output during his final fight against Knuckle was about 1800 aura units, and a punch thrown in that state 150 aura units. This might mean that on average, a Ken punch contains 1/12th of the user's total aura output.
 * A similar calculation may be used to determine a relation between aura output and aura reserves. If Gon's M.A.P. (21,500 aura units) is divided by his output (1800 aura units), the result is approximately 12. However, output is a factor that can vary with training, and Gon's has always been considered exceptional. Furthermore, it used to fluctuate with his emotions. All of this suggests that his values may not be reliable to establish a general law.
 * According to Hisoka, Enhancers and Transmuters have opposite personalities, and they might be attracted to each other because of it. There are several instances of this happening in the series:
 * Gon and Killua: They are best friends.
 * Gon and Hisoka: Hisoka is attracted to and fond of Gon, and has aided (or refrained from harming and/or killing) him on numerous occasions, although the interest is not reciprocated.
 * Phinks and Feitan.
 * Netero and Zeno: According to the latter, they are like "Yang" and "Yin" respectively.
 * It is interesting to note that there are enmity between Transmuters and Enhancers in the series. For example, Enhancers Uvogin, Phinks and Nobunaga didn't get along well with Hisoka, a Transmuter.