Written for the prompt: Scott and/or Jackson come over to see Derek and find Derek and Stiles fucking (the rougher, more animalistic, bitey, knotting, etc the better). Scott/Jackson end up secretly watching them, getting totally turned on and jerking off. Bonus if Derek is totally aware they're being watched and puts on a show (preferably, with Stiles unaware).

Derek had the bad habit of stealing Stiles' phone every time he came over. He didn't have one of his own, and Stiles had never seen a problem with him shooting off a text to someone as long as he didn't rack up minutes or download games...or porn.