Age: 12 (Beginning), 14-15 (Current)
Birthday: July 7th (2011), June 15th (1999)
Height: 158 cm
Weight: 45 kg
Eye Color: Blue
Blood Type: A
Occupation: Assassin (Formerly), Hunter
Nen Type: Transmutation
Equipment: Skateboard, Yo-Yos
Lightning Palm, Thunderbolt, Godspeed, Speed of Lightning, Whirlwind
Killua Zoldyck is the third child of Silva and Kikyo Zoldyck and the heir (former) of the Zoldyck Family. He is the deuteragonist of the series Hunter x Hunter.
Killua is introduced as a character similar to Gon: cheeky, cheerful, and full of bad ideas. However, contrasting Gon's politeness, Killua can be pretty rude to others, mostly strangers and older people. He is also one of the quickest-thinking characters and often analyzes a situation with great ease and accuracy. Despite his young age, his way of thinking, knowledge, and pragmatism give him the attitude of an adult. He is initially very confident about his abilities and able to gauge other people's abilities accurately.
A stark contrast to his best friend Gon, Killua is highly mature in both thinking and emotion. He can keep his anger in check and maintain rationality better than Gon even when facing a terrifying experience.
Despite his horrendous upbringing and the torturous training his family has put him under, Killua has managed to remain generally positive and does not seem too psychologically affected by the pain he's endured.
As time passed, Killua became humble about it and no longer touted his abilities. Despite his advanced knowledge and level-headed nature, he is not very open in general. He will become very embarrassed when Gon openly calls him his best friend or compliments him about their bond.
Killua was born as the middle child of a family of known assassins, the Zoldycks. Showing great promise from birth, Killua followed the traditional Zoldyck training, being an assassin. He had already mastered many killing techniques at a tender age and was set to be one of the best assassins the family had ever produced. At the age of three, he started training in tailing that routinely put his life at risk.
When he was six or seven, he mastered the game of darts as part of basic training. Around the age of nine, he met and attempted to befriend the newly hired Canary (an apprentice butler of the Zoldyck Family). She thanked him for the thought, but she declined his offer to be friends due to their different status.
At an unknown point in his life, his family determined he lacked the mindset of a real assassin and had Illumi implant a special needle in his head to remodel his character through fear subliminally.
Sick of killing, at the age of 11, he rebelled against his family, injuring his mother and older brother, and ran away from home to take the Hunter Exam for fun.
Hunter Exam Arc:
During the 287th Hunter Exam, he met Leorio, Kurapika, and Gon during the first part. After passing all four phases, during the final phase, he encounters his older brother, Illumi Zoldyck, who is disguised as a hunter named Gittarackur.
Killua becomes afraid as Illumi questions his motives, with Killua admitting he does not want to become a Hunter but only challenges himself with the trials. Illumi threatens Killua by killing Gon if he loses his fight, causing him to surrender and return to his home.
Became unresponsive to Kurapika and Leorio's callings, he interferes with the match between Leorio and Bodoro and suddenly implies Bodoro from behind, causing himself to disqualify because of his murder.
Zoldyck Family Arc:
After Killua arrives at his home in the Kukuroo Mountain, he lets himself be tortured by his brother Milluki for three weeks. When Milluki tells him Gon, Kurapika, and Leorio are awaiting him at the butlers' quarters, and threatens to have them kill the three.
Killua is intimidated by his dad, Silva, but slowly opens up during their conversation in Silva's room. During their talk, Silva acknowledges that Killua is his person and not a mere extension of him; Silva has him promise that he will never betray his friends and lets him go.
He reunites with Gon, Kurapika, and Leorio at the butlers' quarters and leaves the house together. They agree to meet again in six months, on September 1st, in Yorknew City. Kurapika and Leorio depart that same day, while Gon and Killua stay together.
Heavens Arena Arc:
Killua confronts Gon about his plans and makes him understand he needs to train if he wants to stand a chance at landing a blow on Hisoka. They fly to Heaven's Arena, where they can teach and earn money at the same time.
They meet a fellow fighter, a young boy named Zushi, and his teacher, Wing. After reaching the 150th floor, Wing warns Killua and Gon against acquiring incomplete knowledge. To make them prepared, Wing takes him and Gond to his hotel room to teach the basics of Nen.
On the 200th floor, they encounter Hisoka and couldn't even get close to him because of his insane bloodlust. Despite his protests, Killua is unable to advance and cannot figure out why. Wing appears behind the two boys and offers to teach them the real Nen.
After learning the natural Nen, Wing started to teach them how to use the basics of Nen. Killua and Gon practiced nonstop to beat their opponents and get ready for the real world.
After receiving the secret message from the box given to Gong by his father Ging, the two decided to go to the Southern piece auction in Yorknew City to obtain the missing part of the message.
Yorknew City Arc:
At Yorknew City, Killua and Gon encountered the Phantom Troupe, having fiery battles with the members to receive the stolen items from the auction.
Later on, Killua, Gon, Kurapika, and Leorio meet up as planned. Kurapika shares his sole reason to be in the Yorknew City, to wipe out the Phantom Troupe. Killua and Gon suddenly got involved in Kurapika's plan but fell through because of the sudden interferences and the immense knowledge and strength gap against the Phantom Troupe.
On September 6th, after their battle with the Phantom Troupe, Gon finds a way to enter the Greek Island, hired by Battera as a player instead of trying to purchase the game, which Killua estimates to be likely to succeed.
During the tryouts for the Greed Island, Killua passes the test quickly while shocking the jury, Tsezguerra, by controlling the electricity at such a young age.
Greed Island Arc:
After entering the greed island, Killua and Gon started on a long and adventurous path to beat the game: Greed Island. The two decided to win the game together. However, they met Biscuit Krueger, their future Nen teacher, and became a strong trio after a short time.
Later on, Biscuit proclaimed herself as their new Nen instructor. Despite Killua's continued protests, she reveals she used to be Wing's teacher after introducing herself. Suddenly the two young rookie hunters found themselves in intense but practical training. Biscuit started to teach them the advanced Nen techniques to boost their Nen usage in a short amount of time.
When they discover it is almost New Year's Eve, Gon reminds Killua of the approaching deadline for the Hunter Exam. Killua meets Kiriko to be able to go to the exam site.
The examiner of the First Phase demands all 1489 applicants battle for two hours and bring him five badges. As soon as he closes the door, Killua proceeds to knock out all the examinees, becoming the only person to pass the 288th Hunter Exam and with no other trials.
Returning to the Greed Island, Killua meets with Gon and Biscuit to continue their adventure.
After a fierce and final battle with the terrorist group named ''Bomber'', Killua places the last card to their book and completes the game with Gon and Biscuit.
The following day they leave Greed Island; Gon converts the card he claimed as a reward to "Accompany," a card transports you to the name in the index you choose to go. Gon's reason to transform this card was because he found out there was a player before Goreniu, the first person they met, written in the book with his father's names anagram.
They greet Biscuit before casting "Accompany," which takes Gon and Killua to Kite in Kakin -not the person they were expecting.
Chimera Ant Arc:
After learning why they teleported to Kite, Ging's old student, Killua and Gon wanted to join Kite's research at NGL.
Later on, the trio engaged in a couple of battles with Chimera Ants in NGL. When they found out this place became a no-man's land, Kite warned Killua and Gon to be extra-cautious. However, Gon and Killua didn't notice Kite's warnings, causing Kite to sacrifice himself to keep them away from Neferpitou, a royal guard of chimera ant king.
The two get dismissed from the mission due to the dangerousness of the area. The two tragically learned their mistake and promised themselves to get stronger to avenge Kite.
Later on, Netero hands him two halves of two tokens, stating that if he and Gon want to join them and continue living as Hunters, they must hold onto them for one month. After that, they learn that they have one month to defeat Morel's two disciples Knuckle Bine and Shoot McMahon, in a battle to rejoin the team.
The boys spend the rest of the month training themselves but didn't get close to win their battle with Knuckle. To accelerate their training, Palm called Biscuit to help them.
On the fight day, both of them lost their battle; Gon lost his Nen ability for 30 days, and Killua finally not be under the auspices of his brother Illumi by getting rid of the needle implanted in his brain. However, when Killua woke up, he found himself with their rivals in NGL.
Both Killua and Gon continued their missions separately to complete the preparations faster to commence the main mission. The Extermination Team met in Knov's sub-dimensional room to start the infiltration.
At the end of the mission, Killua finds out Gon and Pitou went to Peijin. Activating Speed of Lightning, he rushes to Gon's side. As he approaches the hideout, he feels an incredible aura. As his friend stands next to a decapitated Neferpitou, Killua is horrified, fathoming the price Gon will have to pay for that power-up. When Terpsichora manipulates Neferpitou's corpse, Killua intervenes just in time to prevent Gon from being killed, although his friend still loses his right arm.
Gon is taken to the hospital in Swardani City, where Morel and Shoot are also recovering. While his friend is in a deep coma and his condition deteriorates each passing minute, Killua responds to Knov that he will save Gon himself and leaves the hospital, making a phone call.
Killua returns home to seek help from his younger sibling Alluka, whose ability would save Gon from death. When his dad Silva rejected his proposal to meet his sister, he declares that letting his friend die is the same as betraying him, reminding his father of the promise they made.
After leaving the house with his sister, Alluka Zoldyck, Killua calls Knuckle, confidently stating he can heal Gon but may need help to return to the hospital.
Later on, Killua realizes that the escort team is controlled by his brother, Illumi Zoldyck, and tries to flee. After a few light-combat between the escorts and his brother Illumi, he successfully arrives at the hospital to Heal Gon.
When they reach Gon's room, Killua waits for Alluka to wake up, under the careful watch of Tsubone and Amane. After she awakens, Killua tells her that his friend is sick and wants to make him feel better. Alluka expresses disappointment in turning into Nanika again and complains that she never spends time with him. Killua responds they will always be together from now on.
Alluka goes into her wish-granting mode to heal Gon, and Killua asks Nanika to restore Gon to normal. Gon is successfully recovered, although Killua does not tell him he was the one to save him.
Later on, Killua tells Nanika not to come out again, but Nanika couldn't understand what he meant. When he demands it again more forcefully, Nanika, crying, retreats into Aluka. However, when her sister wakes up, she becomes furious with Killua and understands that Nanika is a part of her. Killua apologizes to Nanika, admitting that he was still afraid of Illumi and swearing to protect Alluka.
Killua and Alluka accompany Gon to the World Tree to meet with his father. Killua makes a jab at Gon for his coldness during the palace invasion but is satisfied with his apology. He informs Gon that Nanika was the one who healed him.
He declines the offer to climb the World Tree with Gon, as he will travel the world with his sister. Alluka assures Gon that once she has had Killua to herself for a while, she will let Killua play with Gon again.
Killua retorts he is doing the favor, light-heartedly adjoining that she is what Gon is coming second to. Promising to keep in touch and stay friends no matter what, Killua tells Gon to send his regards to Ging for him, and the two partway.
Not long afterward, Killua and Alluka watch a video sent to them by Gon of a flock of Small-billed Swans taking flights...