I always have a bit of trouble figuring out how to answer questions like this. I’ve gotten them a few times, but like… I’m with Gon in not being too sure what’s considered “kinky”. I’ve seen “kinky” used to describe a wide spectrum of things from the vanilla to the offensive. Gon and Killua are still pretty amateurish when it comes to exploring sex, I think. They may have fucked a lot, and Gon likes seeing other people fuck Killua, that’s established in previous works I’ve done with them. However, they haven’t done a whole bunch of crazy sex, I don’t think. When you’re young, sometimes just fucking is enough. I don’t think Gon sees his taste for being an observer is kinky, though, so I went with something else that’s both kinky, but also easy to do in a way that makes a mess. It sounds like Killua was caught off-guard, even though he asked for it.