He was an assassin, couse hes familly is assassins, but he don't wanted to be assasins. So he went to hunter exam and he met there Gon and other friends, Gon become his first best friend. Killua helped gon find gons dad. he really cares about gon so much but he's too shy to say it and he always when gon says somthing like "killua, i'm glat that you're my best friend" killua always starts blushing, looking away and saying "shut up, idiot" or something like that
