Haruka rubs it a bit more, but he tilts his head to look at Rin's tail.

"Do you feel anything if you hit your tail again something?"

He knows that it isn't the default way that sharks hunt. Still, sharks don't have the obvious scales that the merpeople do, and maybe he still uses it in a fight in case something attacks from behind? Does anything try to attack the sharks? He stares at Rin's tail curiously...