Derek watches Stiles with an almost hungry expression while he strips off his hoodie and t-shirt. He'd meant to only get back to his neck, maybe his collarbone, but the moment Stiles bares his throat like that, Derek's predator instincts kick in and he's on Stiles.
Quick as a flash, Derek has Stiles on his back against the mattress and is nosing at his neck again. Without a shirt is a little better, it gets rid of some of the soap smell (laundry detergent, probably), but it's not quite enough. He runs his hands over Stiles's sides, across his stomach, and up his chest, pressing firmly. "You smell wrong," he grumbles by way of explanation and rubs his face against Stiles's neck with a slight frown.