Killua, Gon, Kurapika, Leorio are 4 very close friends, Killua and Gon are 12 years old, Kurapika is 17 years old, and Leorio 19 years old,Leorio aspires to become a doctor and earn a lot of money, Kurapika wants to take revenge on the entire Phantom Troupe for taking and slaughtering his clan, namely the Kurta clan,Gon wants to meet his father, Ging Freecss, and Killua follows Gon and runs away from his family