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Sam is just pulling her long hair back into a pony tail when Dean enters the room. He knows her far too well since he immediately looks at her with anticipation, according to him her smiles betray her intentions every single time. Which is fine for Sam since Dean can't claim this way that he didn't know what was coming for him.
"You just fucked me four hours ago," her brother whines but can't hide the excited shiver from her that goes through his body.
"Correction. You were fucking yourself on my cock. I didn't have to do anything," Sam says. "I promise, you're going to notice it if I'm doing the fucking."
Dean groans and rubs his half-hard cock through his pants. Sam casually gets rid of her shirt, leaving her almost naked. Only the black bra and the harness with the strap-on in left. It stands proud, waiting for Dean. Sam places her hands on her hips and raises an eyebrow. Watches with satisfaction how her brother's breathing goes faster with a simple gesture like this. He lets out a shaky breath, lips parted and eyes fixed on the strap-on he knows so well.
"Off with the shirt and open your jeans," she orders. Dean hurries to comply. Even puts the T-shirt over on a chair instead of throwing it on the ground.
Walking up to him, Sam stops when they're just a few inches apart and their height difference becomes apparent. Taking his chin into her hands, she lifts it until Dean's looking into her eyes again.
"Were you looking at my breasts or at my cock?" Sam asks softly, knowing how unfair the question is.
"I-i was admiring you," Dean stutters, tries to find the right answer while his brain struggles against the urges of his body. He still doesn't know where the need comes from but seeing his sister with a strap-on never fails to arouse him. Far more than it should since he has never been interested in men. Of course he tested it, anonymously in a shady bar ages ago. Back then he only figured out that dicks don't do this to him.
Sam's strap-on is the only thing that causes him to mewl like a virgin.
"You really can't wait to have inside you again?" Sam asks him, startling Dean who was staring at the black toy again.
She pets her brother's face, then pushes him down and Dean goes on his knees without having been told what to do. This dance is old and well-known to him. Yet he can't but wait for Sam's order.
Taking the base of the strap-on into her hand, Sam guides the tip to Dean's lips. It easily brushes past them as her brother opens his mouth to suck her dick. The following moan is definitely his, caused by his delight of being allowed to suckle at the toy. Yet his eagerness doesn't leave her unaffected. Sam gets wet by watching Dean licking and nursing her black plastic cock and nothing can describe her pride when she sees Dean isn't using his hands to take her deeper. Unable to resist Sam fists her brother's hair to hold him in place when she starts fucking his mouth. Wetness gathers between her legs as Dean's jaw goes slack and he doesn't cock even once until Sam's finished.
Panting through her orgasm Sam lets him go and pulls out of his mouth after she has her breathing back under control. Thankfully Dean doesn't say anything, doesn't comment on how twisted his sisters needs are. (Years and years of hunting can do that to you.)
"Sammy," he says instead. It's just one word, just her name but she hears his plea.
Her own urges satisfied for now, Sam looks down at her brother who's panting harshly, lips wet and parted while his cock is still trapped in his unbuttoned jeans.
"Something you want, brother mine?" Her smile is wicked as her fingers play with the glistening tip of the strap-on.
"Yes," Dean admits weakly and palms his cock through his jeans. "Yes, Sammy. Please."
She bows down to look him into the eyes.
"Remember how I told you that you will know the difference between me fucking you and you fucking yourself on my dick? Get up. I'll show you what I meant," Sam tells her brother and waits for him to scramble on his feet.
To strengthen her words, Sam pulls down his jeans and boxers herself. Dean is naked before he's even straightened his back and there's little better than seeing him swallow nervously. Her brother is aware what's going to follow, what his little baby sister is going to do with him and he has no say in how hard or how fast it's going to happen.
Dean must notice her expression since he takes a step back. He hits the end of the bed and Sam pushes him down onto it without saying another word.
"Are you still loose from earlier?" Sam wants to know and reaches between Dean's legs to check. "Or are you going to need another session with my fingers before I pound into you?"
Dean gulps as Sam takes his legs into her hands and spreads them to have better access to his ass.
"I ... i don't know," he says honestly. Well, he probably could take it. He's used to rough sex and doesn't mind the burn. But Sam usually feels guilty after so he tries to give her an out.
Tapping against his rim, she suggests "Perhaps you should go and find out? Take your fingers and check if your hole is ready for me."
Groaning at the thought, Dean reaches between his legs and circles the rim with his fingers. It's not often he does it himself, it's one of Sam's pleasures but he does know how it works. So he presses the first digit past the ring of muscles and gasps when it immediately sinks deep enough to hit his knuckles. When he starts fucking himself with one finger, Sam lifts his ass with her hands to make it easier.
"Hgn." Dean suppresses a moan while he continues.
"Another," Sam orders. "Use another finger. It isn't enough."
A second finger joins the first and Dean wonders what it most look like. He's fingering himself for his sister who wears a big black strap-on that will go into his ass pretty soon. Encouraged by the thought Dean speeds up his movements, tries to crook his finger like Sam always does. It doesn't have the same effect. Dean whines pitiful, unable to find the spot that Sam always uses to make him come when she does it.
"S-sam, I ... I can't. I want...," Dean pleas, knowing Sam can watch for hours if she's in the mood.
"That depends on you," she answers while staring at the spot where Dean's finger disappear into his ass. "Are you ready now? Ready to get fucked?"
"Yes, ... yes," Dean nods, eager to get on with the show. Truth to be told, he will never be ready but he will also go mad if he has to keep fingering himself in front of Sam.
She pulls Dean's fingers out of her ass, drags him away from the bed until she has him against the wall. With a strength few people know she has, Sam hoists him up until his feet aren't touching the ground anymore and Dean is forced to wrap his legs around her waist. Barely aware of what's happening, Dean clings to Sam's neck as she starts to enter him.
"Oh ... oh god," he gasps as the strap-on pushes past his entrance. Since he has nothing to hold on to Dean feels the stretch more keenly than usual. He's helpless and can only wait while his sisters cock impales him.
"Bear down," Sam hisses and Dean tries, clenching around the prick inside him. It has never been this large.
Sam has never felt so big. Dean has also never been so desperate to come, just seconds after having something up his ass. But true to her words Sam starts to pound into him as soon as she's fully inserted. Fucking her brother against the wall with swift hard thrusts draws sobs from him, desperate noises that show how powerless and vulnerable he's under her.
"P-please, Sam. Please. I can't ... oh god, oh ... oh ... oh," he lets out with each new stab of her hips, grinding him against the wall and the strap-on deeper into his tunnel.
"Not yet," she growls and picks up the pace. "Don't come yet, Dean. You don't have permission yet."
"Hnn, ah ... please, please ... I-i need..." Dean is rocking under Sam's thrusts, almost falling onto her cock.
It's intense. Too much and Dean clings at his sister's neck for help and support who is far from finished.
"You need it harder. I'll make you come like a bitch when I'm done with you," Sam tells him and tightens her grip on his hips. "So ... beg me, Dean."
Dean is taken aback by how the pressure between his legs grows even more. He's close to crying now since Sam's circling her hips, rolling them to mess with Dean's prostate with each shove.
"Oh ... oh, Sam ... yesss," Dean pants. He buries his face in the crook of her neck, hoping she'll take pity on him. But he can still feel the strap-on sliding in and out of him, never stopping and never slowing down.
Until he feels his orgasm building. "No, no ... no, ah ... Sam, I can't ...," Dean howls, breaking down while the strap-on keeps entering him. Over and over again.
It's over the moment Sam forces Dean to look into her face. He comes, a pitiful wail leaving his mouth and clenching around the strap-on that suddenly has stopped moving. Dean rides his orgasm out while his sister has him pinned against the wall. When he finally comes down from it, pain and pleasure slipping away, Dean's aware of the sensation being carried around. He's pliable in Sam's arms and then carefully lowered onto the bed.
Her warmth never leaves him and Dean blinks up at her, his movements sluggish.
"Sammy," he breathes, thankful she's there.
"It's alright, Dean," his sister tells him and strokes his air. "I'm not going anywhere."
Dean mumbles a response, half-asleep already. Only when he tries to shuffle around to adjust his position, he notices that Sam is still inside him. Clenching his ass confirms that the strap-on is in his usual place. Dean falls asleep with that thought.