This is really a strange situation, and he's actually relieved when Ken finally speaks up. It almost makes him want to offer a more immediate response himself. He doesn't do that, of course. He has more restraint than that.

...Ignoring the part where he jumped fifteen feet in a panic. A panic he will never admit to.

After a few seconds of his own quiet thinking, Chikusa murmurs, "It feels better when we're fucking." He tilts his head to the side, considering. "You're there." Which probably explains approximately jack shit, but he's not sure how else to phrase that himself.