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, injuring 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 became 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 is forced to battle in the Heavens Arena martial arts tournament at the age of 6, which he took two years to get to the 190th floor.
Personality
From the outside, Killua seems just to be the rich boy; cheeky, cheerful and full of mischievous ideas. He is also one of the most quick-thinking characters in the series.
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, as many of his adversaries had witnessed and some are not alive to tell about it.
However, until recently, his greatest flaw was to fear those who are more powerful than him, one of whom is 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 struggled with these conflicting ideas during the latter half of the series, as he started to encounter stronger opponents. However, his brother's teachings remained firmly entrenched in his mind, to the point that 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
Hunter Exam Arc
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 he asks how old Gon is. 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.
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 in exhaustion where he is.
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. 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. Kurapika engages in a death match with the next opponent, Majitani, but refuses to kill him after seeing red (literally) and knocking the criminal unconscious. Majitani feigns unconsciousness in an attempt to run out the clock. Leorio and the leader of the prisoners bet on whether he's faking. Leorio holds the man above a long drop, and Majitani wakes up. He concedes the match to Kurapika, but the group loses a large chunk of their time because of the bet. Leorio goes next. His opponent is Leroute, an attractive woman. He loses ten hours in a bet. He then loses the rest of their betting hours to her. Killua then faces Johness the Dissector, a man responsible for the murder of at least 146 people with his bare hands. Killua rips out his heart, explaining afterwards that Johness is an amateur and he is a pro. The last test to get out of the tower has two paths: one is too long and the other will only allow three of the five to enter. Leorio and Tonpa start fighting to see who will stay, when Gon thinks outside the box. 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.
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, Illumi. Killua was manipulated 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.
The Zoldyck Estate 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, 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.
Heavens Arena Arc
Killua and Gon train in the Heavens Arena and learn Nen from Wing, and befriend fellow student Zushi. After having multiple matches in Heavens Arena, Gon eventually gets to fight Hisoka and returns his badge. Gon loses in the end by TKO and Hisoka says that the next time the two fight, their match will be to the death. Killua and Gon leave Heavens Arena after the match and head home for Whale Island, where Gon is given a recorded message left by his father. A ring and memory card are left alongside the cassette tape, and the pair discovers that Ging had created a game called Greed Island. Killua and Gon decide to head to Yorknew City in late August for the Southernpiece Auction in order to win Greed Island.
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. Gon ended 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.
New Hunter Chairman Election Arc
Killua returns home to seek help from his younger sibling Alluka, whose nen 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 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. Morel agrees to these conditions and says he'll construct a private room for them in the hospital's enormous parking lot.
Combat
Weapons and Assassination Arts: In the first part of the series, File:Rhythm-echo.jpg
Rhythm Echo
Killua does not employ or use any weapons in combat. Instead, he relies on several assassination arts passed down to him through his family. These include adjusting his fingernails into claws and the Rhythm Echo.
Rhythm Echo: It is a deadly technique used in critical situations. The Rhythm Echo is a motion that creates an afterimage of the body through a varying cadence of steps. It is a high level attack also called "Technique File:Yoyo.jpg
Killua's Yo-Yos.
of the Dark Step" or "Technique of the Rotating Bodies" because of the 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.
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, weighing 50 kilograms each. 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.
Izutsushi (雷掌 Lightning Palm): The first and most basic ability Killua developed. As the name suggests, Killua is able to shock an opponent by touching them with his palms.
Narukami(落雷 Thunderbolt): A natural evolution of his Lightning Palm ability, Killua is also able to project a large bolt of lightning from his hands, striking an opponent with electricity from a distance. The name of the ability, Narukami, comes from the famous Kabuki play, Narukami Fudô Kitayama Zakura, in which the character Narukami transforms into a thunder god at the end of the fourth act.
Kanmuru (神速 Godspeed): Developed by Killua during his fight against the Ortho Siblings . With his hair, hands and feet changed into electric type aura, Killua's Kanmuru ability allows him to react and move his body at speeds that would normally be impossible (even in Hunter × Hunter universe). This ability changes Killua's aura into a field capable of transmitting all electrical impulses from his brain in a straight line directly to the part of the body he wants to use, completely bypassing his nervous system. It is made up of two parts: Denkō Sekka (電光石火 Speed of Lightning), the ability to move his body according to his own will, and Shippū Jinrai (疾風迅雷 Whirlwind), the ability to sense his opponents movements and have his body react automatically. He can also move from one place to another hastily, as he did when looking for Gon. Kanmuru can only be used for a short amount of time before needing to be recharged.
Trivia
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) did.
He is nicknamed Kil or Killu by his family.
Killua ranked first in all of the 3 character popularity polls that have been conducted so far by Weekly Shounen Jump.
