Killua was standing next to you and you were chatting with Retz and the entire time he was not so silently being jealous because Retz had your attention instead of him

Killua: Gon, can we-

Retz: Gon, wanna hang out with me? I'll teach you how to make puppets.

Killua: Can you go away?!

Retz: ...Gon are you just gonna let him talk to me like that...?