I wrote this for Lydibum, because I am whipped. I don't even ship this usually.

Be aware that this is smut. Lots of it.

I don't own anything, it's all Mofftiss.

He knew it was a bad idea, to keep on doing this, he'd be found out, for sure – his flatmate was a genius, after all. So was his brother, and if anyone could find out, it was he; anyone with control of the CCTV-system would be able to.

But this, this was addicting, and the question was if it wasn't actually worth it. Sometimes he didn't think so, thought that the costs he'd pay if found out were too high, but then they met up and he remembered why he risked everything for this addiction. Maybe it was the same reason he followed Sherlock around London, maybe it was the risk itself that made the risk worth taking.

He was pulled from his thoughts as he entered the flat, a firm body pressing him up against the door, slamming it closed in the process. It didn't take them long to divest each other of their clothes, and soon John was pressed against a bedroom wall, jeans unbuttoned and hands down the back of the other's tan trousers. Perfect white teeth nipped at his bared neck and shoulder as the jeans were unceremoniously shoved down and bunched up around his ankles, John's hands shooting up to grasp at the other's brown hair as he bit down, harsher than before.

This wasn't making love, this wasn't even having sex – this was pure and simple fucking, slaking their lust in the other's body. It was harsh, it was quick and there were no emotions involved. One of them lacked all capability to even feel emotions, and the other wasn't stupid enough to fall for him. Kisses weren't anything they exchanged, that could give the illusion of emotional attachment, and they never – John never, for they always met in the other's flat – stayed after the act was done, and really, this fit them both.

Indeed, the physical relationship, if it could be called that, John Watson and Jim Moriarty shared was simply a... business transaction. John knew that if they ever met outside this, Jim wouldn't hesitate to kill him – or worse – to get to Sherlock, just the same as Jim knew that John wouldn't hesitate in putting a bullet between his eyes if need be.

Jim pulled away from John's neck, keeping one hand on the fair man's cock, stroking, pulling, pushing John towards that exquisite brink, using the other to pull his trousers off. He could feel John's balls tightening, so he stilled his hand, pressing just so with his thumb, enjoying John's half-lidded glare.

"Now, now, we don't want the fun to be over early, now do we?" Jim's smile was positively wicked as he spun them around and pushed John onto the bed. The other man barely hit the bed before Jim was straddling him, John's thick cock pressed against his ass. "Now, are you going to fuck me, or are we going to chat all night?" At his words John seemed to regain some small part of his mind and quickly flipped them over. He bit his way down Jim's chest, soothing the bites with a few strokes of his tongue before continuing, using one hand to grab for the lube as he did so.

He dipped three fingers in the jar as he gave the other man's hard cock a few, almost experimental licks, his own cock almost ridiculously hard from the sounds Jim made – the genius was exceedingly vocal in bed, not something that John minded in the least. As he took the proud erection in his mouth, extremely glad for his lacking a gag-reflex as his nose nestled in the brown curls at its base, he also entered the other man with two fingers – the dual sensations, the pleasure from having John's mouth on him and the pain-mixed pleasure from the fingers roughly entering him, caused a vociferous reaction from the resident sociopath.

It was quick work to stretch the other man enough that he wouldn't be too hurt by John entering him – John had quickly learned that Jim enjoyed, to say the least, a bit of pain with his pleasure. In fact, the more pain, the more pleasure. John released the other's erection with an almost obscene, wet 'pop', withdrawing his fingers and biting and licking his way up the other's body.

"Ready?" John's voice was dark, gravelly with desire and barely-repressed lust as he asked a question he didn't need an answer for. In one quick, harsh thrust he was buried to the hilt in the criminal mastermind, the younger man throwing his head back, baring his neck, keening as John hit all the right spots on the first try.

From there on, they were like a well-oiled machine, John thrusting into Jim, as hard and as deep as he possibly could, rotating his hips at the end of each tortuously slow thrust, Jim scratching his nails down John's back, almost drawing blood.

John released his grip on the sheets to grip and lift Jim's hips, the man's legs wrapping around John's waist. The new angle allowed John to thrust deeper, harder and hit Jim's prostate head on each time, and it didn't take long for Jim to cry out every time John returned and groan each time he withdrew, the doctor gasping and grunting as he gyrated his hips, fingers digging almost painfully into Jim's flesh, most certainly leaving bruises.

It didn't take long, then, for Jim to come, and the way his muscles clenched, massaging John's cock in a most delightful way, quickly drew John's orgasm from him, too, Jim feeling the other man's thick cock pulse in him, sweat running down John's neck as he held himself there, using what self-control he had left to not collapse on top of the other man.

It was in silence they cleaned up, and it was in silence that they dressed. It was how it always was, practically no words exchanged, never calling each other by name, never allowing the risk of forming an attachment to even exist, and that was the way they liked it.

Of course, Jim smirked, almost proudly, over the scratches at John's back, John smiling filthily over the prominent bite marks on Jim's chest.

Right as John put a hand on the door, Jim spoke up.

"Same time, next week. I'll be waiting, Johnny boy." John didn't bother to look over his shoulder at the other man, he knew what he would see. A man, looking almost scarily young, lounging on the bed wearing nothing but a pair of dark-wash jeans, bite marks on his chest and hair in disarray, the man the very picture of debauchery.

John nodded and stepped out of the flat.

Same time, next week. Another week to wonder if he would go, another week to wonder if a short while of relief was worth it – another week to, secretly, never wonder, for he knew.

He wouldn't let himself fall in love, something that would be so very easy, for if he did, then it would be over, this brief amount of time where he didn't have to pretend.

John Watson left the unassuming building, not aware that every move he made was being watched.

Tell me what you thought, yes?