Killua Zoldyck was born as the Son of an assassin family is very well known and feared by many groups ((family zaoldeyk)). Has personalities that are ignorant and like to arbitrarily own. He met with Gon on hunter training, but unfortunately he failed the exam the first hunter because of the pressure his brother, Illumi Zaoldyeck. Because his sister was forced, after tests had come back to Killua hunter homes. Because the determination struggle Gon, Kurapica, and Leorio who risked breaking into the family home in Kururu Zaoldyeck Mountain, then finally Killua Gon had come back together, and from that moment Gon and Killua have never parted.