Killua Zoldyck

Killua Zoldyck (キルア=ゾルディック, Kirua Zorudikku) is the deuteragonist, and best friend of Gon Freecss in the series Hunter × Hunter by Yoshihiro Togashi.

Appearance
Killua has spiky, silver hair and blue eyes. His eyes change depending on the mood that he's in, narrowing and sharpening when he goes into assassin mode. In the Nippon Animation anime adaptation, Killua's eye color is changed to green during the OVAs.

Killua typically wears baggy clothing, with his usual attire consisting of long-sleeved and dark-colored shirts. Most of his clothes have a turtleneck. Killua wears long, baggy shorts in the manga and Madhouse animated adaptation, but Nippon Animation's character design shortened them to reach above his knees. Killua also wears blue boots, recolored brown and black in the Nippon Animation adaptation.

Background


Killua was born as the middle child to a family of known assassins the Zoldyck family. Showing great promise from birth, Killua has already mastered many killing techniques at a tender age, and is set to be one of the best assassins the family has ever produced. Bored and tired of killing, Killua unexpectedly rebelled against his family, injured both his mother and brother, and ran away from home to take the Hunter Exam for fun. He meets Gon during the first portion of the Hunter Exam and becomes great friends. He thinks being with Gon is exciting and adventurous. Killua divulges that ever since his birth, he has been in constant training for the occupation of a professional assassin. Killua had spent years trying to perfect unique skills that assassins portray and possess. He iwas forced to battle in the Heavens Arena martial arts tournament at the age of 6, which he took two years to get to the 199th floor.

Personality
Initially, Killua is introduced as a character who seems similar to Gon; cheeky, cheerful, and full of mischievous ideas. He is also one of the most quick-thinking characters in the series. He is confident in his own abilities, often being humble about it. But when somebody compliments him, especially Gon, he gets easily embarrassed.

However, his ruthlessness and aptitude in killing shows the other side of him — deadly, violent, and bloodthirsty. Having been tortured since birth, Killua has been conditioned to possess extreme tolerance for poison, electricity and pain. He possesses extraordinary agility and strength that makes Killua a one-man killing machine — definitely not one to be trifled with.

Conflicting with Killua's predisposal to kill is his unyielding loyalty to his friends and natural kindness. Oftentimes, Killua suffers immensely in attempts to help his friends without a single complaint. Killua puts others before himself without being concerned about his own health or even his life.

Until recently, Killua's greatest flaw was his fear of those seemingly more powerful than him (one of whom being his elder brother, Illumi). Killua had been trained as an assassin by his brother to be extremely cautious that he only engages in combat provided that victory is absolutely certain. This impeded him as a Hunter, as Biscuit stated more than once that victory is never certain, and that depending on the circumstances, a person has the potential to defeat a stronger opponent.

Killua especially struggles with these dueling ideologies during the latter half of the series, as he begins to encounter stronger opponents. His brother's teachings remained firmly entrenched in his mind, to a point at which Biscuit prophesied that he would one day abandon Gon because of this. Biscuit gave Killua an ultimatum: Defeat Shoot to claim the right to go with Gon and fight the Chimera Ants. Killua lost, and resolved to leave after Gon had recovered from his fight, protecting him in the meantime. Finally he had to face Biscuit's prophecy when he encountered a Chimera ant while Gon (who couldn't use Nen at the time) wasn't far off and had no way to defend himself. Killua made an attempt to save Gon. While fighting with the Chimera Ant, Killua is also battling his inner-self. Preoccupied, Killua is losing to the chimera ant. At the last moment, Killua realized that Illumi had implanted a needle in his brain way back in the first Hunter Exam. This needle was responsible for forcing Killua to retreat and jailed himself on his comfort zone whenever any situation would potentially endanger his life. Upon extracting the needle, Killua was freed from this restraint and gained full control of his subconscious to make his own decision whether or not to flee whenever there is a need to fight stronger opponents.

Plot

1st Phase
Satotz, the first examiner, begins the 287th Hunter Exam with a marathon run down a tunnel underneath Zaban City. Killua ends up next to Gon, and, after antagonizing Leorio for a bit, proceeds asks how old Gon is. Upon finding out, he jumps off his board and introduces himself.

2nd Phase
The second phase of the exam takes place in the Visca Forest Reserve, where the examinees meet Gourmet Hunters (and proctors) Menchi and Buhara. Buhara's test is to find the world's most dangerous pig and bring it back to him so he can eat it. Killua and Gon friends easily complete the task along with 70 other applicants. However, Menchi, the second examiner, baffles the examinees when she tells them to make sushi, a traditional Japanese dish, as none of them knows what sushi is. Menchi overeacts because of an examinee making them all fail as a result, no one passes, which requires Netero to intervene. The test is taken to Split Mountain where examinees hunt for Spider Eagle eggs. At the end of this stage, there are 42 applicants left.

A Game At Midnight
The 42 remaining applicants board the Selection Committee's airship, where it is revealed that their next phase of the exam will begin at 8:00 A.M the next day. As everyone rests up for tomorrow, Killua and Gon encounter Netero. He challenges them to a game; if they win, he'd issue their licenses on the spot. All they have to do is take away a ball from him. Killua eagerly goes first but fails. Gon then takes his turn to take the ball but he also fails. Time passes and when it seems Killua and Gon have tried every possible tactic, Netero suggests they attack together. Though they come seemingly close to it at one point, Netero rockets in between them at lightning speed and takes the ball. Killua calls it quits and ends up killing two applicants in his frustration; Gon, however, decides to play until he forces Netero to use his right hand. When he succeeds in doing so, Gon collapses..

3rd Phase
In the morning, the airship arrives at the top of Trick Tower. The 40 applicants are informed that the objective of stage 3 is to get down from the tower alive within 72 hours. The group is forced to team up with Tonpa.

The first serious test is to win 3 out of 5 matches against tower prisoners. Tonpa takes the first match with a hardened-looking criminal, and promptly gives up. Killua comments on how Bendot would have tortured Tonpa. He would probably rip out Tonpa's throat so that he will never be able to say surrender.

Next, Gon faces the next prisoner, a serial bomber by the name of Sedokan, in a match to see who's candle can burn the longest. As their group struggles which candle to take, Kurapika lets Gon decide, trusting in his instincts. Killua questions this idea, but eventually agrees. After Gon won his match, Kurapika engages in a death match with Majitani. After telling Kurapika that he's a member of the Phantom Troupe, Kurapika holds him up high in the air which forces Majitani to surrender. Leorio is next, facing a psychologist named Leroute. He loses fifty hours in a bet, after losing to her in a Rock-Papers-Scissors game.

Killua confidently faces Johness the Dissector, a man responsible for the murder of at least 146 people with his bare hands. When Johness tried to scare him, Killua boredly asked about the death match. As Johness charges at him, Killua instantly rips out his heart, showing it to Johness and destroys it infront of his own eyes. In the 2011 anime, he returns the heart after Johness' death. His groupmates were amazed, Killua said it was only easy to rip out his heart using his claws. Lippo, as well as Kurapika and Leorio, then find out that he's a memeber of the Zoldyck family. After 3 wins, they have to spend their lost fifty hours in a small room.



The last test consists of one big decision: there are two paths, one is too long that will take all five members but it will take them 45 hours to finish it and the other will only allow three of the five to enter. Killua favors the short one, chastising Gon for wanting to take the long path and saying that he plans on two of the three being "you and me" refering to himself and Gon. Gon thinks outside the box, and they choose the longer path, destroy the wall between the paths with axes provided so they could fight, and all five make it out.

4th Phase
The fourth phase is a manhunt on Zevil Island, wherein the 25 remaining competitors being required to target and acquire their prey's plate. Killua is stalked by Imori for the first three days on Zevil Island, the latter too nervous to strike. Imori's brothers, Amori and Umori arrive to assist their younger sibling but the trio is outmatched by Killua. Killua acquires the badges of all three brothers, throwing the two unnecessary ones away.

Final Phase
The final phase was a tournament with each of the participants. After being selected by the judges as being the most exceptional applicants, Hanzo and Gon face off first. Gon is outmatched when it comes to combat, but his unwillingness to submit causes Hanzo to forfeit the battle — making Gon the first applicant to pass the 287th Hunter Exam. Hanzo knocks Gon out and the boy doesn't awake until the Exam has ended. Satotz fills in the details and explains to Gon that only two people didn't pass the exam —Bodoro and Killua.

It is revealed that Gittarackur is actually an alias for Killua's older brother, into murdering another contestant and subsequently failed the exam. Gon, enraged, confronts Illumi and gets Killua's address. Gon, Kurapika, and Leorio all then depart to Killua's home on Kukuroo Mountain.

Zoldyck Family arc
Gon, Kurapika and Leorio set off to Kukuroo Mountain inorder to retrieve Killua. According to Zebro, Killua opened the third door of the Gates of Trial, which weighs 16 tons. Gon and his friends stay with Zebro in order to train and to open the gates themselves. Then, they met Canary. She was assigned to never let anyone pass her post. It was also revealed that Killua attempted to make friends with her but she refuses. After heavily beating up Gon, she was knocked out by Killua's mother Kikyo, who was accompanied by Kalluto. Kikyo was there to deliver a message from Killua that he can't see them. Before the Zoldycks leave, Gon tells Kikyo to inform Killua that they will stay there for about 10 days.

Meanwhile, Killua was in the isolation room, being tortured by his brother Milluki Zoldyck. It served as a punishment for running away, injuring him and his mother. He tried to cause physical pain to Killua but in no avail, because Killua was sleep the whole time. When he woke up he playfully greet Milluki, much to his frustration. He informed Killua, about the situation of Gon, Kurapika and Leorio arriving to the estate. He tries to taunt Killua stating that he could order those three to have him killed. Hearing this, Killua becomes angry and breaks one of his arms free from confinement. He threatens Milluki he well kill him if he tried to harm them. Fortunately, their grandfather Zeno Zoldyck came and orders Killua to leave and go see his father.

Silva and Killua were having a fatherly talk. His father asked him about the Hunter exam, the people he met, the feelings Killua felt and many more. After Silva asked him if he wants to see his friends again, he says yes. With this, Silva lets Killua go but he has to promise that he will never betray his friends. After this, Killua left and had a confrontation with his mother who tried to stop him from leaving. Killua left his mother, and reunited with his friends leaving the Zoldyck estate behind.



Later Kurapika informed Killua, Gon and Leorio about what Hisoka told him during the Hunter exam, they all agree to meet again in six months in Yorknew City, until that day comes Kurapika and Leorio depart, while Gon and Killua stayed together.

Heavens Arena arc
Killua and Gon went to Heavens Arena, where they will train and earn money at the same time. They meet a fellow fighter, a young boy named Zushi. He eventually became Killua's opponent. While Zushi is in the edge of losing, he suddenly released an amount of aura which made Killua wary and back off. It reminded him of his older brother Illumi, who seems to be using the same technique. After Zushi lost, Killua overheard Zushi's conversation with his master Wing. He was apologizing because he didn't controlled his ability.

Killua then wondered out loud what Zushi was talking about. Gon suggested that they ask Zushi but they barely understood a word he said. Wing approached the three and volunteered to teach Killua and Gon a technique called Nen.

In Wing's room, he was discussing the 4 main principles of Nen. He demonstrated how it works and Killua felt the strong power. After they lesson, Killua told Gon that everything Wing said was a lie.

They finally arrived to the 200th floor. They tried to pass a hallway but to no avail. As they tried to move forward, an employee shows herself. She informed them that they only have until midnight to register for the fight. Hisoka then shows himself. He told them they are not ready to set foot on the floor. Killua tried to fight back but Hisoka used from aura on him. Wing appears behind them and offered to teach them the real Nen. Before they left, the employee also informed them if Killua won't be able to register at the given time, he will never be able to register again.

Back in Wing's room, he demonstrated the real Nen and made Gon and Killua feel the pressure. Then Killua questioned Wing why he decided to teach them and he answered that it would be a big problem if they arrive at the 200th floor without knowing anything. Participants in the 200th floor are all capable of using Nen.

After 2 hours, they went back to the hallway that Hisoka was guarding. While releasing some aura, Gon and Killua finally passed. After Hisoka left, they are confronted by 3 fighters, namely Gido, Sadaso and Riehlvelt. While registering, Sadaso handed out a contract that both Gon and Killua agree on fighting them.

When Zushi was about to be kidnapped by Sadaso, Killua appeared and assured them that Killua will let them win their match. Sadaso then carries an unconscious Zushi back to his room. Before the match starts, Killua enters Sadaso's room and threatens him. After that, Killua is declared winner by withdrawal. When Riehlvelt called Sadaso, he informed them that he will leave. Rievhelt claimed that Killua will never threaten him. Killua is then seen in their room, he informed them to respect the rules.

Killua's fight with Riehlvelt begins. The latter confidently attacks Killua with his electricity, but it failed. Killua developed a strong tolerance of electricity. Killua wins the match easily.

Their training with Wing continues, and Killua found out he's from the Transformation group. After Gon's fight with Hisoka, Gon invited Killua to come back home with him in Whale Island. Killua agreed and they next set off to Gon's home.

Yorknew City arc
The third story arc reunites the main characters for the world's largest auction in a sprawling metropolis called Yorknew City. Killua, Gon,and Leorio try different methods to make enough money to buy Greed Island, a video game that could help Gon find his father. This story arc introduces the Phantom Troupe, a group of thieves who, among many other crimes, slaughtered all the other members of Kurapika's clan. Kurapika crosses paths with them while working as a bodyguard. After aiding Kurapika with the Troupe members, Killua and Gon finally gain access to Greed Island, the seemingly-magical video game that sucks players within. The goal of the game is to collect a number of set cards, although almost everything in the game, from food to money, can be turned into cards.

Greed Island Arc
Inside Greed Island, Killua and Gon are joined by Biscuit Krueger, a master and experienced teacher of Nen who trains them. During their training period, Killua exits the game in order to take part in the Hunter exam and obtain a Hunter's License. Killua displays great tallent in distributing his aura. Gon ends up being the first person to clear the game and, as part of his reward, he is allowed to take three cards to be used in the real world. Using the card 'Accompany', Killua and Gon travel to a player under the user name 'Nigg', who they believe to be Ging. However, it ends up bringing them to Kite instead.

Chimera Ant arc
Alongside Kite, Killua and Gon briefly work as biological researchers in the country of Kakin. As they investigate a giant insect limb found on the country's shores, the group discover it came from a man-sized Chimera Ant Queen — an insect that devours other insects and animals, and then gives birth to progeny that inherit the characteristics of the different species it has eaten. The queen chimera ant washes up onto an autonomous nation called Neo-Green Life inhabited by a neo-luddite culture. The queen quickly develops a taste for humans and builds a colony in order to conceive both an army of offspring and a Chimera Ant King, Meryem. The chimera ants proceed to wipe out most of the population out before Killua, Gon, and Kite reach the nest. They are quickly thwarted by Neferpitou, the one of the King's Royal Guard whom forces Killua and Gon to retreat out of the country.

The queen dies during labor, and the chimera ant king and his Chimera Ants flee the N.G.L., secretly overthrowing the government of the nearby Republic of East Gorteau soon thereafter. Under the guise of the former king of the Republic, the chimera ant king initiates the process of forcibly awakening Nen in the civilians of East Gorteau in order to form his own personal army to conquer the world — resulting in the deaths of millions unable to awaken Nen. As ants formerly under the queen's rule rejoin the king, the Hunter Association mobilizes quickly to stop the oncoming genocide by sending in an extermination team of Hunters to East Gorteau. Distraught over the murder of Kite at the hands of the Royal Guards, Killua and Gon join the extermination team in order to take revenge for their friend. After some encounters with Youpi and Pouf, even seeing the King from the distance who was to be fighting Netero himself), Gon finally meets Pitou, and at the end, seeing that all Pitou was doing was deceiving Gon from not being able to save his friend Kite, Gon unleashes all the anger and sorrow he was keeping within him, turning into an older version of himself. Using all his potential in one instant to kill his enemy. In the aftermath, he was to lose something important (perhaps just all the years he lost) and was unconscious by releasing such tremendous power. Killua then took him to the rest of his friends. Gon currently resides in a Hospital with the rest of the hunters that survived the invasion on the Chimera Ants. The Doctor tells Knov and Knuckle that Gon is in an extremely dangerous state, and requires life support. The Doctor thinks to himself saying he's never seen something this gruesome happen to a 12 year old boy in a single night.

13th Hunter Chairman Election arc
Killua returns home to seek help from his younger sibling Alluka, whose nen ability can help save Gon from death. After convincing his father, Killua finally gets to see Alluka. The two siblings are happy to be reunited with each other. Killua remembers the time when he was young and Alluka displayed his wish-granting abilities to their servants. Silva and Kikyo asked Killua about this to which he told.

Back to present, the three requests of Alluka are done and Killua has to make a wish. Silva, Kikyo and Milluki are watching through a surveillance camera in Alluka's room. Milluki regrets the computer wish because it was so easy. Silva glares at him and Milluki apologized. Killua asks Silva to open the door for him and Alluka. His father refuses, saying that he has to make a wish inside. Killua makes a request to Alluka that if they are not able to leave the mountain together within 30 minutes, Alluka will kill their mother Kikyo. Alluka agrees and Silva has no other choice but to open the door. Kikyo slumps on the floor, thinking that Killua could say something so cruel, he has already grown and is somewhat proud of him instead.

Killua calls his friends back at the hospital and tells them that he's going to take care of things. He calls Gotoh and asks him about the Restriction Movements. After a while, Gotoh and Canary accompanies Killua and Alluka. Gotoh asks Killua if it is necessary to take Canary with them, he replies that Alluka is a "girl" and Canary will be able to take delicate care of Alluka. However, Silva ordered Tsubone and Amane to come with them as well. But before they could go, Alluka requested for Tsubone's pinky fingernail. She gladly gives him and tells Killua that she will conceal herself for now. In that way, Alluka will be unable to make a request to other people.

On their way to meet Gon, Killua's butler Gotoh receives a call from Leorio, asking to speak with Killua. After they have an argument, Gotoh lets Killua on the phone to tell Leorio to listen. Gotoh then tells Leorio to make it so that when they arrive Gon is the only one in the hospital. Leorio cant agree with these conditions so he hands the phone over to Morel. He agrees to these conditions and says he'll construct a private room for them in the hospital's enormous parking lot.

As Killua, Alluka and their bulters are on their way to Gon, Illumi calls him using a phone and asks him if had already taken out the needle in his brain. Killua verified it and his brother told him that "he will beat him at his own game". Soon after, a truck crashed into their car which causes them to fall off a cliff. Killua protects Alluka as Illumi and Hisoka watch from afar. When they decided to split up, Hisoka asked Illumi if he could kill Killua. Illumi gets angered, and warns Hisoka. In the dense forest, Killua sensed his brother's terrifying murderous aura. Amane suggests to stay away from Illumi as possible and they ran off. Killua suspects Amane as Illumi's cohort, but the latter assured him that she and Tsubone are not his enemies. She also told Killua that Silva and Zeno are not the enemies, their mission is to keep Killua safe. But Killua counters that as long as Alluka's safety is not one of their mission priority, they will remain as his enemies.

Killua uses his Godspeed ability to escape their butlers with Alluka. While running away, Tsubone is seen following them. When they stopped, Alluka asks him if he is only a hindrance to him and if it wasn't for him, Killua will be able to get along with the other family members. Killua reassures that everything will be well and he will always be with Alluka. After sensing that someone is actually watching them, Killua and Alluka leaves the scene.

As the two Zoldycks continue to escape, Killua uses Godspeed to escape Tsubone. But she uses her nen ability that is fast enough to keep up with Killua. Tsubone, Amane and Canary follow them by a motorcycle but Killua escapes them by jumping off the cliff where the motorcycle can't follow them. He later reaches an airport and rides an airship in order to escape Illumi who is probably watching them from afar. Killua calls Morel about his plan on "selling" off Illumi. Morel thinks Teradain Neutral and Bushidora Ambitious will consent to it and many other Hunters would like to lend a hand. They plan on capturing Illumi's needle humans first. The other Hunters agree on this plan and whoever comes close to the airship will be captured. And Illumi makes his first move by using his needle humans.

Killua then contacts Canary while still inside the airship. He asks her to tell Hishita, another Zoldyck butler to send out cars to three locations as well as near the hospital where Gon is. Killua and Alluka land where Hishita is waiting with a car. Killua tells Hishita to drive them to the hospital but then needle-controlled humans appear and surround the car. Killua is surprised at how his brother could have possibly known where they will land. He orders Hishita to continue driving, but the latter informs him that he cannot do it unless Master Illumi tells him so.

Killua finds Alluka and himself surrounded by Illumi's manipulated people. Killua out of concern of Alluka's safety has become hesitant on the idea on fighting or escaping as well as puzzled on how they were followed which was answered by Tsubone who revealed that it was due to a hidden camera that was placed on her that was being watched by their Mother and Milluki, where the latter was sending the feed to Illumi's phone. After Tsubone completed the last two requests Alluka has entered the wish granting state but used the wish to heal Tsubone's hand insted to show Illumi that there is no harsh consequence later on when asking Nanika a wish that requires healing and threatens Illumi that if he keeps referring Alluka as an object then he will disown his eldest brother. Hearing his explanation that there would be no risk for the family, Illumi agreed that he will now allow them to continue on their quest to save Gon but warned him that the entity called Nanika is still very dangerous and will never allow Alluka to be fully free until Killua tells him why he is the only one that can make consecutive wishes on Alluka's ability (First was the kiss after they left the mountain and the second was healing Tsubone's hand making it two wishes in a row).

Finally, Killua is able to reach the hospital. While he waits for Alluka to wake by himself, the two of them stay in Gon's room. After Alluka wakes up, Killua tells him that they are in the hospital and that his friend is sick and wants to make him feel better to witch Alluka respondes by saying that he doesnt want to turn to "It" again and wants to stay with Killua, Killua manages to convince Alluka by saying they will always be together, Killua wishes for Gon to return to normal, Alluka goes into wish granting mode and starts to heal Gon.

When Alluka switches to Nanika, she requested Gon's hand to touch it. When Killua grabbed Gon's hand, he was shocked to see it so damaged, and he begged Nanika to save Gon. Upon starting to heal Gon, a huge energy emits from Nanika, which is so powerful that everyone in the vicinity can feel it. It is shown later that Alluka succeeded into healing Gon. Subsequently, Killua was seen still in the hospital with the unconscious Alluka in his arms with Illumi approaching. Illumi hypothesizes the conditions to activate Alluka's ability and tells Killua that if he is able to control Alluka's ability as well as Killua can, he can guarantee a minimum level of freedom for Alluka, instead of being locked in a room. However, Killua states that he is going to protect Alluka no matter what, and he wakes Nanika up and asks Nanika to make Illumi go home and Illumi is immediately teleported back to the Zoldyck's residence. Killua then requests Amane and Tsubone to leave the room too or he well ask Nanika to do the same to them. Both of them leave voluntary, while Nanika playfully tells Killua to be a good boy. Killua told Nanika not to come out anymore, but Nanika refused, stating that she likes Killua. After brief argument which cumulated in Killua yelling at Nanika not to come out anymore, Nanika compiled with tears in her eyes. Killua embraced Alluka while apologizing to Nanika and stating that now Alluka can be free. Alluka resurfaced but is mad at Killua for making Nanika cry, and says that if Killua want to protect her, he should also protect Nanika. Killua regains his senses and thanks Alluka for 'waking' him up. He then asks Alluka to call Nanika out and he apologizes, stating that he was afraid of the idea of Illumi controlling Alluka and making her do evil. He states that he will protect both of them and tells Nanika not to grant any more wishes. Nanika forgives Killua and both of them embrace with tears in their eyes. Tsubone is told by an unknown person (presumably Silva) that the movement restriction order on Killua is cancelled.

Combat

 * Claws: In the first part of the series, Killua does not employ or use any weapons in combat. Instead, he relies on several assassination arts passed down to him through his family which includes adjusting his fingernails into claws. These claws are sharper than knives and can tear a limb easily.


 * Rhythm Echo: It is an assassination art. The Rhythm Echo is a motion that creates an afterimage of the body through a varying cadence of steps. There is a total absence of noise during the movement and multiple phantoms. In the Nippon Animation adaptation of the anime, the Rhythm Echo is changed into an ability that allows Killua to disappear into the darkness. According to Netero it is the advanced version of the "silent gaits" technique.

In the manga the yo-yos have a six point star or hexagram design on them. The hexagram design is used in many various religions and cultures including Islam, Christianity, Occultism, Hinduism and especially Judasim where the hexagram is the symbol used for "The Star of David". In the Greed Island OVAs the Hexagram or Six Point Star is changed into a Pentagram or a five point star. However later in the Chimera Ant Arc, Killua is seen using a yo-yo that has a pentagram on it. Since Killua has two yo-yo it is most likely that one yo-yo has a hexagram while the other has a pentagram.
 * Yo-Yos: During the Greed Island story arc, Killua begins using yo-yos made of a special metal alloy in combat. The yo-yos are extremely durable and heavy, each weighing 50 kilograms.They can be used in conjunction with Killua's Hatsu as well. Killua is reluctant to use the yo-yos in combat, thus using only his raw physical abilities in order for his opponent to know as little about his combat abilities as possible.

Nen Abilities
As a Transmuter, Killua's most efficient in changing the form of his Nen. As such, Killua developed a Hatsu in which he transmutes his aura into electricity. This feat was both inspired and made possible by the years of electric shocks he received as a child, both as training against torture and as punishment from his older brother Milluki. In order to use the ability, Killua needs to charge himself by absorbing electricity through a socket.

Trivia

 * Killua ranked first in all of the 3 character popularity polls that have been conducted so far by Weekly Shounen Jump.
 * Killua is the 3rd Transmuter in the Zoldyck family, after Zeno and Silva. Coincidentally, all three have silver hair.
 * Killua's name in Japanese is written as "Kirua" in katakana. It combines the Japanese transliterations of the English words "kill" (kiru) and "killer" (kira).
 * Killua's eye color shifted in the 1999 series; though initially dark blue, his irises became green in the OVA series. In 2011 series, his eyes are back to dark blue.
 * He once stated that he doesn't know how to write letters, but he had written a "death notice, Zoldyck style" before. Another kind of letter is used for blackmailing people.
 * He hates red peppers. He was invited to Gon's house and Mito forced him to eat the red pepper but he spit it out.
 * Favourite Food: Kokorobokun (Chocolate balls).
 * Killua occasionally is drawn with catlike features (paws, ears, mouth) in humorous situations, much like Botan of Yu Yu Hakusho (a previous work by the same manga-ka) was.
 * He is nicknamed Kil or Killu by his family. However, neither the Zoldyck's employees or Gon and his friends use this name.
 * Hiei, one of the main characters from YuYu Hakusho, bears some similarities to Killua.
 * Both of them had went through tragic childhoods, killing people at a young age, and being submitted to torture.
 * Just as Hiei can conjure up fire and manipulate it since childhood, so does Killua utilize electricity and can even create it from his own aura. This ability was based off of the immunity Killua had developed during a long childhood of electrical torture.
 * Both are extremely fast
 * Hiei was ranked on first place for most popular character in the Yu Yu Hakusho manga, Killua had also won first place in the Hunter X Hunter popularity votes.


 * Killua enjoys exploring cockpits and drinking tea.
 * Killua was slapped two times by two different women: Aunt Mito and Biscuit Krueger.
 * Killua's yo-yo's may have been derived from Rinku, a secondary character of Togashi's other series YuYu Hakusho.
 * The 2011 series added some scenes where Killua and Canary first met as children. He also tried to make friends with Canary, but he never tried to offer her an animal skull.