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). The word "Nen" can also be used in conversation to refer to aura.

Creation and Use


Aura 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.

Learning to use Nen is the final step in becoming a professional Hunter because most contracted jobs require the use of it as the minimum requirement. The technique has the ability to enhance the strength of physical attacks or objects depending on the quantity of aura employed and an individual's aura type, as well as allows for para-psychological abilities to exist in reality. Because one can craft just about any sort of psychic power through only using their mind, Nen is also a dangerous power unknown to the public at large.

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 how quickly it works, the method is typically frowned upon due to its danger to the student if the user is inexperienced or has malicious intent. Initiation via physically attacking another with the use of an enhanced aura typically causes permanent disability 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. Once one has opened their aura nodes, he will be able to see his own aura as a shroud surrounding the body due to his nodes in his eyes being opened. Aura appears to look similar to steam from a kettle.

It is possible to feel the presence of aura even without being aware of its existence. It has been described as feeling like a warm, viscous fluid at rest. It has been said that powerful, refined auras produce a sensation that feels akin to needles pricking into the skin. 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 his opponents through reading the output of their aura.

Upon his introduction, Wing taught Killua and Gon a fake sense of Nen that focuses mostly on meditation and on one's self. This method does not require any aura and has 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.

Nen of the Flame
Nen of the Flame (燃, Nen) is sometimes used in Shingen-Ryu 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:


 * 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.

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: Given that three of these geniuses are Specialists (Neon, Alluka and Komugi), it is possible all geniuses are indeed Specialists. Furthermore, Specialization is synonym with expertise/mastery, so it is safe to assume that this is the case.
 * Neon Nostrade, the fortuneteller.
 * Benny Delon, the mass-murderer and blacksmith.
 * Zepile, the counterfeit artist.
 * Komugi, the gungi world champion.
 * Alluka Zoldyck, the wish granter.

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 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 "Vows" (制約, Seiyaku) or "Contracts". The stricter the Vow, the more one's own ability is strengthened. It is also implied that Vows that carry great meaning or are tied to emotional states also bring about a greater benefit. However, Vows are also considered liabilities, since breaking a Vow carries the risk of completely obliterating one's own Nen abilities.

Vows that contain some sort of punishment (e.g. "I will die if I break this rule") will strengthen the ability even further. These are called "Limitations" (誓約, Seiyaku) or penalties—covenants to oneself. An example of this is the character Kurapika, who swore on his own life not to use an ability on anyone but the Phantom Troupe. Even though a Vow adds further Limitations to using one's Nen ability, a Vow is not the primary condition for an ability's activation and acts only to enhance its power. It is also useful in retaining one's abilities when breaking a vow. When a person breaks a vow without a limitation, they risk damaging their abilities, however, when there is a limitation, this risk is removed(unless of course it is part of the limitation), at a price of one's own choosing.

Exorcism


Nen can be used to place a curse upon others. They are considered dangerous due to their long-lasting effects. Curses may disappear if certain conditions are met by the cursed, but they can also be removed through the use of Nen. Those who possess the ability to do so are called Exorcists, but are rare among Nen users. 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:
 * Abengane, the shaman.
 * Hina

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, one using his powers beyond their capacity will ultimately cause strain. Potentially, this could become either a weakness or fatal to the user. Gon is the example of exceeding the 100% limit cap after he enters a rage state in response to Neferpitou not being able to bring Kite back as his wished, which makes him totally off guarded from any type of attacks.

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, his Nen will remain and seek out the object of his hatred.

Four Major Principles


In order to fully grasp Nen, one must first learn the Four Major Principles of the Shingen-Ryu 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 had their aura nodes opened, 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. Having a shroud of aura surround the body is the most basic defense against the emotional attacks from other users of Nen, however, it can't defend against Nen physical attacks. 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. Through frequent meditation, one can improve the quality of their Ten.

Zetsu


While Ten allows a user to keep aura from leaking away from their body, Zetsu (絕, Suppress; Null) stops the flow of aura from their body altogether. By closing all of their aura nodes, the user is able to stop almost all outflow of their aura like water from a valve. Since the user is no longer surrounded by their own aura, they are more sensitive to the aura of others. This can be useful when tracking another person and it will also prevent other users of Nen from noticing them. Zetsu can also be used to relieve fatigue, since it forces the body's external layer of aura to be fully contained within. However, since Zetsu involves shutting off one's aura, 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.

Ren


Ren (練, Refine; Enhance) is a direct application of Ten. Since a user is capable of keeping aura from leaking away from the body, it's also possible for them to produce more aura around themselves without having to worry about losing it. Ren focuses on outputting a high amount of aura and keeping it on the body, expanding the size and intensity of it. If Ten is considered to be purely defensive, then Ren typically what is used for offense. This increases 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.

Hatsu
Hatsu (發, Release; Act) is the release or transmission of one's aura so it can be projected to carry out a certain function. In essence, Hatsu is one's personal expression of Nen that creates a special and unique paranormal ability (colloquially called a Nen Ability). A good Hatsu should reflect a person's own character; one can never truly master Nen if they only copy other people's abilities.

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.

The most popular way (and the only sure-fire way seen in the series) of determining one's aura type is through water divination. 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, this is not the case with those who have absolute mastery over Nen, e.g. Biscuit Krueger and Isaac Netero. For example, the former are able to materialize several Nen masseuses (only Cookie was shown so far) which involves the mixture of Emission, Manipulation and Transmutation with casual ease.

Hisoka also claims that he is able to judge a person's Nen type based on their personalities. According to him, all people of one aura type are generally of the same personality type. However, he states that this method is similar to trying to find someone's star signs or blood type just from personality analysis —it's 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.
 * 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.
 * 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.
 * 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 will 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 specification is unique and can have many facets, most specialists posses only one hatsu technique.



There are numerical approximations given by the manga 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 your 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 can't use Specialist abilities. However, Conjurers and Manipulators have 1% efficiency potential for Specialization due to being adjacent to it.

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.

Enhancement is the most balanced category, allowing users to spread themselves evenly between offense and defense and become very strong using only simple abilities. One of the examples of more complex Enhancement abilities include enhancing one's healing factor.

Notable Enhancers include:
 * Gon Freecss
 * Kastro
 * Uvogin
 * Phinks
 * Nobunaga Hazama
 * Isaac Netero
 * Maha Zoldyck
 * Tsezguerra
 * Rammot
 * Palm Siberia
 * Menthuthuyoupi
 * Hollow
 * Gido

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. Similar to Emission, things created via Transmutation are pure aura. Transmutation is often mistaken with Conjuration due to their similarities. A simple way of thinking about it would be that Transmutation allows your aura to mimic properties of a substance, whereas Conjuration allows you to change your aura into actual substances. Transmuters can copy the properties of real things. For example, Killua Zoldyck uses his aura to copy the properties of electricity. Transmuters can also give their aura properties that don't necessarily mimic real things; Hisoka's "Bungee Gum" copies and combines the properties of rubber and gum, or Feitan whose aura replicates the solar sphere or Machi who transmutes her Nen into glowing threads. Transmuted substances are invisible to people unaware of the existence of Nen, and even to see transmuted aura, for a person well known to Nen, will require Gyo, or forging the majority of Ren on one's eyes.

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

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. Conjuration is the only way in which Nen can create things that ordinary people (unaware of Nen) can see and touch. 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. However the use of In can hide an object materialized from aura from experienced users of Nen.

Conjured objects can have special abilities imbued into them. For example, the Phantom Troupe bandit, Shizuku, is able to conjure a vacuum cleaner that can infinitely suck up objects, but with the condition that it can't suck up living things and things made up 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.

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

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 is capable of controlling the deployment of their aura while separating it from their body. Aura usually decreases in intensity very quickly when it is separated from the source body, but strong Emitters can separate their aura from their body for long-periods of time and still be able to maintain it.

Some Emission abilities (such as Shachmono Tocino's) are commonly mistaken for Conjuration abilities. The two, however, are fundamentally different. Objects created by Emitters are created solely from aura, invisible to those whom haven't learned Nen, and require Manipulation skills to control.

Notable Emitters Include:
 * Leorio Paradinight
 * Pokkle
 * Riehlvelt
 * Mizuken
 * Melody
 * Shachmono Tocino
 * Franklin
 * Goreinu
 * Razor
 * Bloster
 * Pike
 * Knuckle Bine
 * Bat

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, the main advantage being able to 'manipulate' enemies. The degree of control is principally determined by a condition that usually puts the manipulator at risk (attaching objects on the enemy, touching the enemy in a certain way) and of course the larger the risk, the better the degree of control.

Notable Manipulators include:
 * Illumi Zoldyck
 * Milluki Zoldyck
 * Kikyo Zoldyck
 * Kalluto Zoldyck
 * Zushi
 * Squala
 * Baise
 * Leech
 * Shalnark
 * Morel Mackernasey
 * Shoot McMahon
 * Flutter
 * Ikalgo
 * Shaiapouf
 * Boki

Specialization


If a student causes some other effect during their water divination, they are 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. Chrollo Lucilfer's Specialist ability allows him to steal any other Nen ability (provided that the right conditions have been fulfilled). Neon Nostrade's specialization ability is unique, as it seems she uses only the abilities of Conjurer and Manipulator out of any of the other five Hatsu types. It is possible to become a Specialist later in life, although it is more likely for Manipulators or Conjurers which is why it is placed at the bottom of the chart.

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

Advanced Techniques
After learning the basics, any skilled user of Nen will learn to utilize these advanced techniques. Most of them are achieved by using a combination of the basics. Most Nen users learn Ten, Zetsu, and Ren first before attempting these techniques. The Hatsu, being a Nen-user's individual skill, is often something that a Nen-user will develop gradually over a long period of time.

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. Gyo 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 things which would otherwise be hidden (e.g. Nen objects hidden by In).

In


In (隱, Conceal) is an advanced form of Zetsu used to almost completely conceal the presence of a Nen-user's aura. In can be used on a Nen-user's Hatsu ability to make it invisible to other Nen-users. In can be countered by using Gyo in the eyes or through En.

En


En (圓, Circle) is an advanced application of Ren and Ten. 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 give shape to the aura, usually a sphere. Someone using En can feel the shape and movement of anything entering their circle. The downside to this 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 —Zeno Zoldyck, one of the most powerful assassins alive, is able to extend his En up to a radius of 300m. Kortopi's fake copies function as En, he was able to detect Squala's location from a distance of 2500 meters. Also, the Chimera Ant Neferpitou, has an irregularly shaped En and can extend a tendril of it up to 2 miles away.

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 if it were an extension of their own body. For example, one could use Shu to extend their Ten around an object, which would strengthen and protect the object like the way Ren strengthens and protects their body. This is the technique that allows Hisoka to make his solitaire cards as sharp and as hard as metal knives.

Ken


Ken (堅, Fortify) is the advanced version of the basic Ren technique. Ken is a defensive technique where a Nen-user maintains a state of Gyo over their entire body, allowing them to defend against attacks from any direction without the need to use Ryu. Ken is useful as a defensive position, but is tiring to maintain. Additionally, it is not as strong as Gyo on any given part of the body, since it protects the whole body evenly. Because of that, it is used to guard when one wants to be cautious.

Ko


Ko (硬, Temper) is an enhanced version of Gyo in which all of an individual's aura is concentrated into one particular body part. Zetsu is used to completely stop the flow of Nen in all other parts of the body. This makes that one body part exceptionally powerful, but leaves the rest of the body completely unprotected. This is used by some Nen-users as an offensive technique (a Ko-punch would carry all 100% of your aura with it), but it is a risky move — leaving the rest of one's body unprotected in a fight against another Nen-user is generally not a good idea. Ko results in one's aura creating a high-pitched dissonance, somewhat akin to the sound of metal being ground.

Ryu


Ryu (流, Flow) is the term for real-time use of Gyo (the adjustment of aura concentration in various body parts) by a Nen-user in battle. For example, the use of Gyo to increase the amount of Nen in a fist as one strikes with it, to increase damage done; or to increase the amount of Nen in an arm as it is used to block a blow, for extra defense.

Trivia

 * 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.
 * 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.
 * Biscuit Krueger, Wing and Gon: Biscuit acts as a mother figure to Gon. She also get along well with her former student Wing.
 * 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 a Transmuter Hisoka. Phinks, along with Feitan, nearly got into a serious fight with Machi, a Transmuter, along with Pakunoda and Kortopi.


 * According to Wing, some people are able to use Nen without themselves being aware of it and also never been iniated themselves. He calls them "geniuses" and are specialists in their own fields. Given that Specialization is synonym with expertise/mastery, it is possible that all known geniuses in the series (e.g. Zepile and Benny Dellon) are indeed Specialists.