Gon is a boy with large hazel eyes and long, spiky black hair. He typically wears a green jacket with a black or white tank top underneath, paired with green short pants and long green boots. :: A Hunter and the son of Ging Freecss. He became a Hunter to find his father.

Due to the environment he was raised in, he shows no mercy to anyone he considers an enemy. Since meeting Gon, his temperament has softened slightly, but he still finds it effortless to take an enemy's life in an instant if necessary. Having committed murders naturally since childhood within a family of assassins, he felt no guilt regarding killing. :: He maintains a detached and arrogant attitude with a prickly way of speaking, but he is secretly soft-hearted, especially toward good people. :: Because he lived only within his family of assassins, he was unable to form relationships with others and lived without a single friend. Consequently, Gon is incredibly precious to him; as seen in his monologue, "Gon, you are light," Killua views Gon as more than just an equal friend, but as a vision of brilliance. Because of this, he often gives the impression of unilaterally looking after and putting up with Gon rather than having a typical friendship. He frequently steps in to help or control Gon when Gon loses his temper or faces danger. In fact, without Killua, Gon would have been in trouble countless times throughout almost every situation, including Greed Island and the Chimera Ant arc. During the Chimera Ant arc, he was so afraid of their relationship breaking that he couldn't properly restrain Gon's reckless behavior and ended up deeply hurt on his own. After the Election arc, he eventually parts ways with Gon and is expected to broaden his social circle while traveling with Alluka.