He laughs softly, recognizing the defiance, even - on some level - delighting in it, but just as quickly as it came it's gone again. He slides his hand to the back of Dean's head, curls his fingers into hair and drags it back, and begins to cut.

It's shallow, really hardly a break in the skin at all, but more than a scratch. A single long, graceful, sweeping slice down from the corner of Dean's right collarbone and across his chest, followed by another, and another, until he's lost in the careful delicacy of it. Parallel cuts, cuts that cross, some done quick and some achingly slow. At last he releases Dean's hair and drops back into a crouch, framing Dean's ribcage with his hands before he begins to drag the edge of the blade down over the bumps of his ribs.

Too much in the way of even shallow wounds and they'll have a problem on their hands. But this is just enough.