They have nothing so mundane as a romance, and Molly isn't quite sure what to call it within the confines of her mind. She supposes it should bother her, their arrangement, but in all honesty it suits her far better than whatever dull life her mother wants for her. She only finds it awkward that she can't find the label for them: relationship is too heavy, but fuck-buddy is juvenile and they aren't friends, not really.
He always seems to know when she needs to be taken apart, scraped raw and bruised with the press of his fingers into the jut of her hipbones, or tangled roughly in her hair, or clutching at her waist. Well, he would, wouldn't he- Sherlock bloody Holmes, with his pale observant gaze, always tracking the pinch of the lines around her eyes without actually looking at her.
Molly knows what everyone thinks of her, sees the pity in their eyes each time Sherlock snaps at her and steals body parts that will undoubtably land her in hot water should their absence be discovered. She can hear the susurrus of DI Lestrade's irritation, his short huffs of frustration and the shift of his clothing as he folds into lines of exasperation at Sherlock's blatant rudeness. They think she is little more than a lovesick doormat, swept up in the mad miasma of long legs and blue eyes.
She doesn't correct them, doesn't care enough. What is the well of pity in Sergeant Donovan's eyes, compared to the sheer pleasure of bring Sherlock Holmes to his knees with a few well-placed tugs of his dark curls? What does she care of the blank, judgmental gaze of Mycroft Holmes, as she wraps her legs around Sherlock's waist and sinks down onto his cock, forcing choked moans from his throat as she marks his beautiful skin with her tongue and teeth and nails?
The sex is spectacular, naturally, in spite of Sherlock's endless elbows and knees, and they even work out a system for cuddling that doesn't feel nearly so intimate as she'd feared. They lie about her flat naked, talking (mainly Sherlock, but Molly enjoys the sound after too many hours in her quiet morgue) and touching. She's surprised how much she likes him in those moments, no matter how many ridiculous deductions come spilling out of his mouth; she's equally surprised by how often he requests her presence, considering the nuclear levels of hatred that exist between them whenever they're both clothed.
He stumbles in occasionally after a hard case, collapsing at her kitchen table with his fringe over his face, and she fixes the disgustingly sugary tea and toast dripping with two types of jam that he craves. Molly honestly does not understand how he can be so thin, and she glares at him over her own mug (tea with milk) until he eats everything she's given him. He sweeps her off to bed, or the shower, or the couch, or up on the tiny countertop, and leaves bruising kisses on her collarbones and shadows of his fingers around her hips, always hard and fast and glorious.
Only when they're alone, entirely alone, in the privacy of Molly's flat- outside, anywhere, he's cold and she's hopeless, just as they agreed. He's arranged it so carefully (not even my brother can know, he'd said, examining the ends of her hair for a case while she melted in orgasmic bliss into the mattress) and his words and sneers would hurt if she didn't know exactly the way he moans when she presses her teeth into his shoulder.
It's worth it, for her, because she knows she'll never fall in love with her miraculous madman no matter how perfectly he fucks her, not when she's seen him laid out and shivering across her sheets and wanted nothing more than sex (and to feed him up because really, how many sharp points can a person have?). She doesn't care about the drugs, not enough to say anything, because who is she to discuss his choices? He doesn't care about her hideously poor choice in boyfriends and telly, and she thinks that's fair. She likes that she knows him, better than most (perhaps better than anyone)- enough that the moment she sees him with Dr. John Watson, she knows before he does that all of it will be coming to an abrupt end.