The whole thing was more suddenly forceful than Sasuke had been expecting, and a gasp of surprise blew out of his mouth when his back collided with the wall. But, fuck, he was not complaining. His eyes wrenched shut when teeth dug into his neck; the sound that escaped next was part moan, part yell... part pain, all pleasure. The fingers twined in Sam's hair curled hard, fisting close to the scalp. But not tugging, no impedance to the bite - or anything else Sam would decide to do, wherever he decided to move his mouth next. Just holding, grounding, as Sasuke groaned a little lower and rocked his hips with just a little more fluidity, a little more control.