Gon and Killua hit it off from the moment they meet simply because they’re boys of the same age who haven’t had friends before. Their pure friendship is built on pushing each other to overcome the next obstacle ahead of them and enjoying their ongoing adventure. It’s their unique circumstances that allow for their friendship to thrive: because Killua was raised to be a cold-hearted assassin, friendship is something he longs for and is eager to treasure; Gon, who is simple-minded and straightforward, is deeply affectionate towards those he regards as friends.

While Gon is determined to find his father, Killua is simply happy to go along with him and help Gon achieve his goal. They become supportive of each other, and although a rivalry is initially teased, all sense of competition between Gon and Killua becomes friendly and a mutual desire to push each other to be stronger so they can deal with their increasingly tougher obstacles. For Gon, their friendship grows to the point that he starts to consider Killua as his best friend and is eager to introduce him to his father.

Kite, the student of Gon’s father, dies protecting Gon and Killua from Neferpitou, the obscenely powerful Royal Guard of the Chimera Ant King. Gon blames himself for the loss of Kite and believes that his weakness is what led to Kite being captured, not yet aware that he was killed. Although Gon dedicates himself to the goal of saving Kite and tries to remain optimistic, the loss is devastating enough that Gon starts to become emotionally troubled, especially when he sees that Kite’s body has become nothing more than a mindless puppet.

While trying to save Kite, Gon’s morality often comes into question. When Gon finally confronts Neferpitou, he’s enraged to see Neferpitou caring for another person after they’d mercilessly killed someone Gon cared about. He mimics that trait when he threatens to kill the girl Neferpitou is caring for if he suspects the Royal Guard is playing a trick on him. After Neferpitou reveals there’s no way to heal Kite, Gon sacrifices his health and years of his life to obtain the strength necessary to defeat Neferpitou. His willingness to give up everything for vengeance shows how much one loss can mean to him.

The relationship between Gon and Killua takes a turn for the tragic after the loss of Kite. Killua’s inability to help out Gon in his moment of need pushes him to the point of tears, and Gon doesn’t realize his behavior is affecting the one friend who has always stood by his side. During his tense showdown with Neferpitou, Gon even questions how much Killua cares about Kite when he tries to stop him from doing something he would regret, taking the life of an innocent person. The sight of a pained Killua receiving biting remarks from his dearest friend was enough to make even the lovable and understandably angry Gon a hated character for viewers.

Despite the troubling development to their friendship, Killua never gives up on Gon and goes out of his way to revive Gon after he falls into a coma in the aftermath of defeating Neferpitou. Killua finds himself forced to confront his greatest fears, namely Illumi, his older brother, to wake up Gon. Fortunately, Gon apologizes to Killua for his behavior when he wakes up and their friendship promises to continue to grow thereafter.