When it comes up to Sherlock, John is at loss. The madman would get John doing all kind of absurd things for the sake of The Work or some strange experiment. It's all fine, he said once, unaware of it being a damned self-fulfilling prophecy. Now they just had sex and it was very good, thank you and for inexplicable reasons John was perfectly fine with that too. Of course it wasn't related to the Work, neither to some sort of experiment. Sherlock wouldn't do this, it sounded just out of character. (truth be told, pretty much as sex, but again, who knew?) Why then were they casually sprawled over the world's only consulting detective's bed as it was trivial, something they would do any day? John wonders. Maybe because Sherlock wanted to and he could do it and oh, it's all fine. They both wanted. John wasn't much sure since when he started to want so much (he could not recall), neither if they would do it again. (lots of reasons for don't, lots for “go on” and many more for “it's all the same”). It does not matter, really. Ignorance is bliss, they say. Furthermore, right at that moment John Watson is far too tired to think about what the hell.
“Come back,” he mutters grumpily when Sherlock leaves his side. It's cold and Sherlock is very warm. Too lazy to open his eyes, John listens to the detective searching for something inside the nightstand's drawer. “What are you doing?” he asks.
Sherlock chuckles in his unique manner and pulls himself close to John again. The doctor sighs, content in being warm again. He startles when something cool and slightly piercing is suddenly pressed against his stomach's skin.
“it's just a biro.” Sherlock explains as this was perfectly reasonable. John curses again but allows Sherlock go on with this writing-on-john's-skin thing. It's not the first time he was used as a notepad anyway.
“Done,” Sherlock announces, his tone too malicious for John's tastes. John finally opens his eyes and looks down. Small letters adorn his belly just below his navel. They read: “This good doctor belongs to the world's only consulting detective.”
“Don't you?” Sherlock asks while nuzzling John's ear with his nose.
Resigned, John breathes in and out.