Killua and Gon both cosplayed together a lot. Duos like: Angel Dust and Husk, Sonic and Tails, Naruto and Sasuke, Nino and Adrien, Will and Mike, Hua Cheng and Xie Lian, Bakugo and Deku, etc. They went to a cosplay convention as Hinata and Kageyama. Killua got all dressed up as Kageyama, bought a volleyball, bought a cape and crown, and everything. He bought crow wings for Gon and helped him style the wig.