[Gon had literally just said that Kite would kick Leorio's ass up and down for being a jerkhead idiot about transition related stuff, but is suggesting it for Alluka. all he can do is give an exasperated sigh. at least Leorio and Killua know each other, though...

and THEN—

Killua looks so incredulous it's just fuckin' off the charts.

then he comes back to reality, looking feral as he shouts at Gon.]

You idiot!! You can't just—"tell"!! I mean, with some people, you might be able to... It's just better to not assume anything about anyone, I guess. Just like you'd never know Alluka was born as a boy, some people you'd never guess only like the same gender.

Generally... I don't think you can tell.

[why does Killua look kind of crestfallen when he says that]