[He knows that the question doesn't demand an answer - he's asked such questions himself. The answer, of course, is that Kaworu keeps finding the places he chooses to lavish with attention strange (his ear?) until the sensations that follow nearly drive him insane. How else would Axel know about such bizarre sensitive points? He's surprised that his body reacts so much like a regular Lilim body - as much as it may look like one, it's still Angelic in structure.
He jerks his hips up again, frowning a little at the slowing.] Why do you keep starting and stopping?