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Dean knew it wasn’t exactly normal to be in love with your home security AI. But C.A.S., the Central Authority System for the Winchester household, wasn’t exactly a normal AI. Cas had been junked by his previous owners. Dean had found him while scrap diving at the local dump, a dangerous way to make a living considering how uncaring drone bots could be about non authorized users that might get swept up with the scrap metal they constantly carted away to be melted. Dean had almost lost an arm trying to drag what was left of Cas’ android body out before they both got dumped into the fire.
Like all the best machines Cas had attitude. Once Dean had gotten him up and running it became clear that there was some sort of fundamental programming error in Cas that caused him to disregard the Winchesters as users and treat them more like misbehaving, but cherished, programs. Sam sometimes argued that Cas should have a full systems update, but in general it was Dean who suffered the most at the hands of Cas’ constant fussing. For an android with a barely passable human casing he could do mother hen really well.
Cas worried about things like Sam’s late night internet addiction and Dean’s eating habits. Especially Dean’s eating habits. He would set all the food dispensers to vegan only because “the number one cause of death in white males is heart disease Dean, and your saturated fats intake far exceeds the daily recommended amounts”. Dean took this about as well as anyone could expect and tried to override the system, but Cas was, among other slightly worrying traits, very smart –he should be since Dean has been tinkering with him for years, building in illegal upgrades and making adjustments ever since he found Cas in that junk pile -and Cas caught Dean red handed, giving him a jolt right to the shoulder because “many mammals learn to avoid undesirable actions through selective amounts of negative conditioning”. Sam decided to join team ‘evil robot overlord’ that day, just laughing his ass off when Dean came in rubbing at his shoulder and yelling over-dramatically about how Cas was trying to kill him, to which Cas responds by giving him a death glare.
The reality of it was that Cas was completely, pathetically loyal. Because Dean was the one who saved him, who helped him to function again, who put the time and energy into giving a shit about what happened to him. Cas would never do anything to hurt him. Permanently that is. Electrocution in calculated amounts was something Cas ran the math on, and it was only acceptable because Dean can’t be trusted to make reasonable decisions.
Which was perhaps the mindset that let the two of them to fall into their current relationship. Even artificially intelligent computers couldn’t always force their humans into behaving in perfectly safe and healthy ways. It took several instances of Cas pushing too hard at Dean over something or another, his disturbing proclivity for saving people at the cost of his own well being with no regard for the consequences to his family for example, before Cas realized that he couldn’t proceed as he had initially intended. When pushed too far on his invisible and deeply repressed boundaries Dean tended to lash out emotionally. He yelled, cussed, and occasionally threw objects. Cas would have given little heed to the physical violence of the outbursts, Dean never did more than threaten to put Cas in hibernation—a complicated measure to enact and one he never showed any signs of actually initiating—but Cas was surprised at how…unpleasant he found himself feeling when Dean was truly mad at him.
Eventually he worked out a system of human care that worked for both of them, one that allowed Cas to spend as much time with Dean as he wanted while Dean was kept out of trouble and got to indulge in being the center of someone’s undivided attention. Plus there was the sex. Lots and lots of sex.
So Dean had balked at first when Cas had begun to court him. Who ever heard of an AI deciding he wanted a human boyfriend? It was weird, and Dean couldn’t see what Cas got from the whole arrangement. Cas had worn him down with a tactical application of logical argumentation and a surprisingly thorough knowledge of blowjobs. After the first week Dean gave up wasting time arguing against it and decided to spend time making upgrades for his new boyfriend instead. Testing these new upgrades took time too, of course.
They had been at it for hours now. Cas had fucked him satisfactorily to orgasm before pulling out his bag of toys and staring up between Dean’s legs beseechingly.
Cas had a fascination with inserting things into Dean. He could spend whole nights slowly fucking Dean senseless with any one of the fat dildos he had mysteriously collected over the last few months. Dean, to his own surprise, found that he didn’t mind this at all. Cas was gentle, more fascinated with the sight of Dean’s stretched and greedy hole than in roughing him up. Sometimes Dean felt like some sort of science experiment, as if Cas were forming theories on the human physiology and systematically testing all of them on Dean’s body. Needless to say he didn’t let himself feel too guilty in letting Cas indulge his curiosity.
Dean felt wet fingers pressing in, the robotic clicking and shifting of joints inside of him causing a whimper to escape as it stretched his already sensitive body. At the sound, Cas quickly moved to sooth him, running his free hand comfortingly down the hunter’s thigh as he brushed soft kisses to his knee. Slowly, he felt himself relaxing again.
“More?” Cas asked, his tone hopeful and just a tiny bit begging. Dean made a contented sound in agreement, too blissed out to form words at the moment. With a happy little wiggle Cas settled down, pulling out a basic blue toy a little larger than his own well-endowed dick (hey, Dean didn’t create the thing, but could he really be blamed if he got his AI some pricey upgrades?). Dean simply laid back, spreading his legs comfortably wider. He was ready to enjoy whatever made Cas happy tonight. He made a little sound of surprise as the toy traced his hole lightly. He heard Cas chuckle as more lube was drizzled onto the opening and the toy moved in easily. He was still nice and open from their fun earlier and Cas seemed content for now to watch the easy slide of the plastic as he moved it in and out of his lover. Dean almost missed it when Cas switched the toy for something larger, feeling the stretch as just another sensation as Cas murmured endearments into the cleft of the hunters thigh.
They had never used such a large dildo before, and Cas was careful to go slowly with it. He was rotating the toy now, his thrusts shallow as he seemed intent on stretching out every inch Dean’s hole could take, smoothly pressing against his prostate as the toy made each circle. In spite of himself, Dean could feel his dick give a halfhearted twitch at the sensation.
Cas sighed happily, leaning in to press a kiss to the crease between Dean’s hip and groin, tilting his head to watch the toy sliding into Dean. The toy felt huge, and Dean felt like his body was made of stars. He blinked dazedly up at the ceiling as his body tingled pleasantly with each inch of plastic Cas pushed into him. His AI was setting a random pace with this larger toy, pushing it in just a bit before pulling it out further. In a little, out a little, in a lot. On and on as Dean floated in his electric haze.
In all the times that they had played this way before Cas had learned that the more lube the better if he wanted to drag out the time he could spend exploring Dean’s body. As much as Dean could love the burn and stretch of prep, Cas was far more interested in the way that he could turn the man into a blissful melted body of contentment with a little extra attention and a gentle touch. He was, as Dean suspected, compiling a list of all different ways Dean’s body responded to various stimuli. Of course, his favorite part was discovering a completely new reaction, and he was excited to see what he could discover with this newest toy.
He pulled the toy half out to apply more lube. Carefully he twisted it back into place, hungrily watching the small twitch of Dean’s hips that the sensation brought. His human was thrusting up slightly with every twist of the toy inside him, his dick thick and bobbing as he humped the air. With one precise movement Cas pushed the toy in up to the base. The full stretch of the huge toy thrusting in caused Dean to gasp, pressing desperately down on the toy before jerking up as he tried to fuck himself on it.
Unprepared for the enthusiastic reaction and distracted by the lovely, flushed look on Dean’s face, Cas lost his grip on the dildo.
The toy slipped out, catching slightly on Dean’s rim. Dean whined, a puff of surprised breath at the sudden, all-encompassing feeling of emptiness, and came hard all over his stomach.
For a moment the only sound in the room was Dean’s soft, wet panting as Cas slowly sat up and back on his knees. The AI stared down at him, unblinking and still in the way that only non-organic things could be.
Suddenly Cas grinned, flopping forward to crawl over Dean with a laugh. Dean just whimpered slightly as Cas brushed against his oversensitive dick before laying across Dean to kiss and nuzzle along his jaw.
“Amazing,” Cas hummed into Dean’s neck. He settled in, pulling Dean tightly to his chest and sliding two fingers into the sloppy mess of his hole. Dean made an agreeable noise and relaxed bonelessly into Cas’ hold as sleep overtook him.