Note: yeah, I don't have to explain that this is not the end, do I? (part 1, part 2, part 4, part 5, part 6, part 7)
So John lay awake, considering getting out of bed, but as soon as he moved, Sherlock held on tighter. Then he considered getting himself off, but Sherlock’s elbow was blocking him; probably on purpose. What Sherlock hadn’t thought about, though, was that John could still reach his arse. For a few long seconds, Sherlock didn’t show any reaction, but when John slipped his hand under his waistband and squeezed, he pressed his face against John’s shoulder; and, even though it should have been physically impossibly, pushed his elbow down a bit so it nudged John’s erection. John cursed and squeezed harder, making Sherlock’s elbow press down a little more. All the while John was sure Sherlock was asleep. If teasing had become part of his reflexes, John was doomed.
In one quick move,he turned around and reversed the position in which Sherlock had teased him. Now Sherlock spooned John, and John tried some wriggling, all the while his hand remained on Sherlock’s arse. It didn’t take long until he could feel sweet success pressing against his backside and with a grin he slipped a hand into his sweatpants, stroking himself to the rhythm he held up.
Sherlock awoke with a gasp, and immediately tugged his hand out of his pants and plucked the other of his arse. “Don’t even bother.”