S1E41 : Bungee × Punch × One Round Battle

Gon and Killua learn their types of Hatsu; Gon is an Enhancer and Killua is a Transmuter. Gon fights Hisoka, and while over-matched, gets a punch in and gives back the number badge that Hisoka gave him during the exam. After that, Hisoka fights with his full power.