There's a Muggle market not far from Grimmauld Place. It sells records, old books, odds and ends of Muggle clothing. Sirius likes it there. It's where he found his favourite leather jacket, crushed beneath a pile of stained bell-bottoms and moth-eaten jumpers. He sneaks off to Diagon Alley every so often to change a few Galleons for Muggle money, which he forced himself to master because he knew how much it would annoy his mother. Not that she'll ever know. The goblins give him odd looks, but they never say no.
He hardly every buys anything, anyway. Mostly he wanders around, fiddling with the costume jewellery, or flicking through the records and trying to remember which ones Moony likes. Sometimes he watches the people. Muggle fashions are brilliant, especially compared to wizards', whose idea of cutting-edge elegance is to maybe add a slightly curlier fastening. Once, he sees a girl dressed in what looks for all the world like a nightgown his mother might own over a pair of black combat boots. Another time, a man walks past in a spherical fur hat bigger than his head. With his dog collar and battered leather jacket, Sirius blends in perfectly.
A pair of girls go by, arm-in-arm, and giggle and duck their heads as they catch his eye. One of them looks back over her shoulder at him and smiles. She looks sort of like Remus, with crinkly hazel eyes and curly hair. He winks outrageously at her, making her turn bright red, and goes back to looking through a pile of dog-eared posters. There are various bands, one of the Osmonds with random shiny white teeth coloured in and creative moustaches drawn on in pen. His eye is caught by a huge, glossily black motorbike, crouched in an empty road like a predator. He has three similar ones already, stuck up with his best Permanent Sticking Charm, but he buys it anyway and continues rifling.
Someone seems to have donated an entire collection of girls in bikinis, some spread out over car bonnets, some bending over, pressing their breasts together as they grin fixedly into the camera. Most of them have that bloody stupid hair like Mary MacDonald has, with the ends flicking out around their faces and big, puffy, sweeping fringes. Their bodies look swollen, glistening, strangely unappealing. For some reason, he thinks of Remus, his dry, rough hands squeezing his shoulder, his shirt pulled tight over the muscles of his back. Sirius feels a wave of something like nausea. He shoves the whole collection at the girl behind the stall, who raises an eyebrow but says nothing. The posters cost nearly all of his precious Muggle money, and are unwieldy to carry home, sticking out of their plastic bags. After the first six or seven people stare at him as he goes by, he realises that he probably should have asked for the posters to be rolled inside-out, but it's started to rain, and sitting down in the middle of the wet pavement to wrestle with extremely unwieldy pornography is not very high on his To Do List. Sirius pulls one of the posters out and holds it blank side up over his head to keep off the rain, no longer caring whether or not people stare.
He fumbles for his wand, nearly dropping everything, and taps the doorknob, muttering 'Toujours Pur' through gritted teeth. The lock clicks loudly and disapprovingly. He tries to ease open the door as quietly as possible, but it creaks all the way like a banshee and he swears under his breath. He gets about halfway to the stairs before Regulus appears in the drawing room doorway, pale and breathless with excitement at having caught him in something so obviously incriminating. His gaze flicks to the bag in Sirius' hand.
'What are those?'
'Get lost, Regulus.' Sirius strides towards the stairs, but Regulus darts out from his doorframe and snatches one of the posters. Sirius whirls around to grab it back, but Regulus has already unrolled it. His pale eyes widen as he takes it in, the spread of the girl's legs as she sprawls over the car bonnet, the perfect O of her shiny pink mouth. Not like he'd have any interest in that sort of thing anyway, the little poof, Sirius thinks sourly. He tries to pull the poster out of Regulus's hands, but he hangs on with typical limpet-like grip. 'These are Muggle,' he whispers. 'You've been going to that dirty place again.'
It strikes Sirius as more than a little funny that Regulus is horrified first and foremost not by the pornographic nature of the posters, but by the fact that they don't move. If it were dearest Bella squirming all over that car, Mummy would be breaking out the elf-made wine.
'Fuck off, you little freak', he snaps, and sprints up the stairs, ripping the poster out of Regulus' spidery hands as he goes. The floorboards moan and complain under his feet, and at least three of his ancestors stir in their paintings to mutter obscure curses at him before he reaches his room. He knows perfectly well that Regulus will tell his mother about the posters as soon as he gets the opportunity, so he locks the door behind him and puts up the posters as fast as he can, covering every bit of wall space he has left.
The hammering on the door starts just as he's putting the Permanent Sticking Charm on the last poster, the one above his bed. The charm on his door holds out all of ten seconds before there is a bang and the door crashes open, smoke trickling from the lock. He lies back with his hands behind his head and watches in silence as his mother storms around the room, firing every curse she can think of at the posters and shrieking all the while about filth and dirty Muggle whores and how any son of mine. Sirius' only contribution, when she seems to be running out of steam, is to ask whether he really is a son of hers, because he honestly can't see how. His mother slaps him hard and backhanded across the face and sweeps out, leaving the posters untouched and a bruise from her heavy emerald ring blossoming on his cheekbone.
His dusty blankets are heavy, weighing down on him as he wriggles out of his pyjama bottoms. He strokes his cock half-heartedly and tries to focus on one of the girls. It doesn't matter which. They're all more or less interchangeable anyway, same bouncy hair, same bouncy breasts, same wet pink mouths. But like before, they seem exaggerated, cartoonish, almost ugly. He tries to picture them touching him, stroking his cock, but instead, unbidden, comes the ghostly feeling of rough, strong fingers and the press of a strong, scarred chest against his. He comes suddenly, before he fully realises what he's thinking about, and lies awake for hours before he drifts off to sleep.
Every night that week, he starts jerking off thinking of the girls and finishes thinking of Remus. By the last night, he's given up on the girls altogether.