Kisame could refuse to answer, but he sees no reason not to.

"Process of elimination doesn't give much to tell, kid. I know the clans well enough to tell which of them you aren't, and of the remaining, Yuki is the most likely. Knowing a Hoshigaki's skill, you didn't back away from the little puddle I made. That's because the water is as much a weapon for you as me, eh?"

Though outwardly relaxed, Kisame is coiled like a spring inside. This is about the time when a conversation like this would dissolve into a fight. Or not, but that's part of the fun.