Derek pushes Stiles back until his knees catch on the edge of the bed and the teen tumbles on to it, startling a laugh out of him. He puts a hand on each knee, spreading Stiles' legs enough that he can slip between them and lean over the boy, kissing him gently.
“Are you sure about this?”
He already has Stiles naked and prepped. Had bent the boy over the kitchen table, slipped finger after finger in him until he'd had Stiles stretched around four and his thighs shaking as he moaned helplessly into his arms. He doesn't think Stiles will ask to stop, hasn't smelt anything but arousal since the teen walked in the door, but he wants to make sure.
“I've been sure of this since July, dude.” Stiles snorts, honey brown eyes meeting his own in challenge.
Ah, July. When Lydia had allowed the entire pack over because, as she claimed, they had needed a break from all the alpha pack shenanigans. She hadn't been wrong and Derek had almost not gone, too concerned over finding Erica and Boyd and determined to ignore the nebulous thing that had started up between him and Stiles. He ended up going and it had been worth it, if only for the scandalized expression on Scott's face once he caught his and Stiles' combined scent after they'd spent much too long wrestling in the pool.
He takes a moment to pull off his shirt, the only item of clothing left on either of them, and in the time it takes him to do that Stiles has apparently decided that now was the time to hold a condom in Derek's face. He's not sure where the boy got it in his naked state, but it had been Stiles who had the great idea of grabbing the lube off the table before they came to the bed, and his clothes had been on the table near it, so he had to assume that he'd carried both over.
Stiles was always thinking ahead like that, but this was one area where Derek just had to quirk an eyebrow at the teen. Stiles starts to frown so he snorts and flashes his eyes at him and, oh, that is an interesting quickening heartbeat, isn't it? And Stiles is smart, even as he squirms a bit, glances from his red eyes to the condom in his hands, he seems to be understanding what Derek is saying without saying. That he's a werewolf and that they didn't catch diseases like that.
Stiles rolls his eyes, “Alright then, Mr. Alpha, what about cleanup?”
Derek leans his face towards Stiles' and makes sure he has his attention when he grins and lets his tongue run across his upper teeth. The boy's eyes darken at that, the sharp scent of arousal suddenly getting thicker as a drop of precum leaks from his slit. Stiles lets out a deep breath, squirms in his place caught between Derek and the bed.
“What sharp teeth you have, Grandma.” Stiles aims for deadpan but it comes out breathless as he spreads his legs seemingly unconsciously so Derek can fit more snugly between his thighs.
He snorts and puts his hands on Stiles' hips. The teen seems to get the idea, lifting them and allowing Derek to put a pillow under his lower back. Stiles uncaps the lube and lets a generous dollop fall into the palm of one hand, which he then reaches grabs Derek's erection with, getting him nice and slick. He helps guide Derek to his entrance, hand only leaving him when Derek's pushed slightly inside.
Derek puts a hand under each thigh and lifts Stiles' legs so they can rest on his shoulders, making it easier for him to bottom out. He lets Stiles have a moment to adjust, instead leaning down to catch one of the already slightly swollen nipples in between his lips so he can graze it with his teeth gently and enjoy the way he gets a small appreciative sigh.
“You good?” Derek pulls back to ask and Stiles scrunches up his face at him.
He's gotten used to that facial expression. The I-hate-that-he's-asking-but-he's-just-trying-to-be-nice one-and-I-want-to-encourage-that, as Stiles himself had called it, so he rocks into him in retaliation, drawing a small groan.
“You know,” Stiles adopts his talking about the weather tone, the one he knows pisses Derek off the most. “I expected that my first time with an alpha werewolf would actually make me feel something. Turns out it really is just like my dildo.”
Derek growls and allows his eyes to bleed red again. He kisses Stiles to shut him up as much as it is to shift his position, tilting his hips up and drawing out carefully. He tries a few thrusts out, moves his hips once more, and can tell he hits the jackpot by the way Stiles almost yelps, back arching so hard that he's surprised he doesn't hear a crack.
Now that he knows where the boy's prostate is he hits it relentlessly, speeding up until Stiles is clawing at his back and cursing him with each new breath. Stiles throws his head back and his wolf howls inside of him at the sight of that long neck. His fangs come out almost of their own accord at the display; he's so used to always wanting to claim Stiles that he's not surprised.
He licks at the teen's neck, feels the rapid beat of his pulse through the vein there, grazes his teeth over the pulse point just sharp enough for him to feel. It makes Stiles tighten around him, makes eager hips lift to meet the harsh slap of his own.
“Derek, fuck,” Stiles whines, bares his throat more to encourage him, because of course the little shit knows it drives him wild. “I need...”
“What do you need?” Derek asks, kissing down the teen's chest. He slows his thrusts and allows himself to slide in deeper, so Stiles can really feel him. “Need to feel my fill you up? Want to feel me lick it out of you?”
Stiles groans, “Just touch me!”
And that's a reminder of just how much Stiles is giving over to Derek. The teen has never been the patient sort, especially not when it comes to gratification, and here he is letting Derek give him as much pleasure as he wants without once trying to touch himself.
So Derek rewards him and wraps a hand around his cock, only needing to stroke it a few times before Stiles climaxes. He takes the opportunity to rut into Stiles now that the teen is loose with his orgasm, sucking one of those sensitive nipples into his mouth just as he finds his own release and thinks of ownership, of equals and pack and running under the full moon together.
He takes a moment to just breathe, resting his head on Stiles' chest and listening to the rabbit quick heart that beats so reliably inside of it. Stiles lifts a shaky hand and runs it through his hand, contentment wafting off of him in waves. Derek smirks and kisses his chest again, just over his heart.
“So, did I beat the dildo?” Stiles huffs, but his lips quirk up at the edges and Derek feels a thrill of satisfaction at that.
He kisses his boy's stomach, laps at the drying cum there. Stiles' stomach tenses and he tugs at Derek's hair, but he's not fooled. He can already smell the arousal coming off Stiles, slowly and almost lazily, and then quicker when he gives an experimental thrust inside of the loosened passage. He's lucky that Stiles is still a teenager. It'll make him a lot more willing to let Derek continue to cum inside of him.
There's old stories. Dark tales of forced love and forced turnings. Of sexual copulation that would almost guarantee a human turning; the bite had a risk of being denied because a human was rejecting what was happening to them. Usually the human had no idea that they could reject anything with copulation—if it happened to be forced there was the rejection of the act itself, but not of the change.
It's not- Derek doesn't know for sure if it works. Sure, there were stories, but lots of things were just stories. Like the kanima. Like the specific way for an alpha to insure that they might escape from death.
So he wasn't sure. But his wolf already fought him over whether or not to claim Stiles almost constantly, made his gums itch with the urge to bite whenever he was around his boy. Because Stiles was his, had been since Scott had left him out of the plan for Gerard.
And Derek- He needed someone he could trust. Pack.
There was a time when he never would have pictured Stiles as the perfect packmate, as the perfect second for him. But that was before his own betas abandoned him, before Scott's betrayal, before he saw how loyal Stiles was. Now he knew that once Stiles chose someone he gave and gave and gave, that he seemed to almost inherently know what pack was, knew that he should be getting back from Scott and never was.
But that was okay. Derek would make sure they took care of each other, even more than they already had been. Stiles would be his and he would be Stiles' and no one else would matter. He'd be strong enough for him because Isaac still hadn't gone over to Scott completely and because Peter refused to leave Hale land. And he knew that Stiles would watch over him in return, would challenge him and not be afraid of him.
He knew that they'd be good together.
A knock on the loft door is what rouses him from the light doze he'd fallen into. The quicker than normal heartbeat lets him know that it's Stiles and he wakes up quickly at that realization. It's not even been four hours since he'd left to sneak back into his own house. The smell of them was still thick in the room, soothed Derek enough that he wasn't immediately jumping to his feet and throwing the door open.
Instead he took a moment, let his senses hone in on Stiles. The scent that was seeping under the bottom of the door—there was something warm to it. Something he's not smelled on Stiles before, but screams of pack, of mineminemine, and his heart does a worrying kind of flop because this is happening a lot quicker than he had assumed it would.
He steels himself and makes his way to the door, opening it and taking in the sight of Stiles before him. He's standing with his hands loose at his sides but Derek can see the way he's shaking, the almost unnoticeable tremor that wracks those long fingers. He reeks of anxiety and subdued anger and Derek almost stops breathing entirely when he takes in the way the teen's eyes are flickering from brown to gold.
He doesn't smell of fear or pain, but then again he wouldn't. He hadn't been bitten.
“What—what the fuck, Derek.”
It's not a question. It's not exactly a demand, either. It's pure confusion—the reaction to something happening that Stiles had never planned for himself, and certainly never without knowing why. Stiles' voice is hoarse, like he needs a drink of water.
From what little Derek knows it very well may be true. The change will be burning him fever hot inside; if he reached out a hand he wouldn't be surprised to find Stiles running hotter than normal. Of course, this is a fever that won't stop. After this he'll always run at about 101 degrees, like almost every other werewolf. That's okay, though. He won't have to deal with actual fevers anymore because he'll never get sick again. At least with no human disease, anyway.
Stiles was turning fast. He'd probably be a full werewolf in a little under twenty four hours—from what little Derek knew that was quiet a feat. Most didn't fully complete the transition until a couple of days had passed. He'd forgotten that Stiles was a spark. It had probably made the transition easier, more noticeable, and once Stiles noticed, he believed. And once Stiles believed, well...
The question then was did he believe he was Scott's or did he believe he was Derek's?
Derek stays silent, steps back from the door and heads for the kitchen to pour Stiles a glass of water. He knows the boy well enough at this point to recognize the slightly glazed look in his eyes, knows that even if he did say something right now that he probably wouldn't hear it, even if his wolf is growling at the thought that Stiles might already be including himself in Scott's beta pack.
“I just... woke up like this,” Stiles says a bit helplessly, stepping inside and shutting the door behind him automatically. He walks to the bed, sits down heavily on it and runs both hands through his hair. “You didn't bite me last night,” he points out, throat so dry that Derek can hear him struggle to swallow properly. “And no scratches, either. There wasn't anything...”
Derek walks back to Stiles with the glass of water and stands in front of the teen. He grabs one of his hands and pushes the glass gently into it; Stiles' eyes leave the floor and clear a little, a split second of irritation flashing across his face before he chugs the entire thing and returns his gaze stubbornly to their feet. His grip is so tight on the glass that it's already cracking, spiderwebs traveling along the sides.
“It's my fault,” Derek says, because the words fall easily from his mouth by this point. Because Stiles doesn't leave, because he stays where he is, glass gripped so tight it's almost breaking, breath held as he braces himself for a betrayal. “There's stories that if an alpha wants enough-” here Stiles takes a deep breath, releases it slowly “-and spills his seed inside someone receptive, that they could turn.”
The glass doesn't shatter. Stiles stares at the ground, measuring out his breaths carefully. In-1-2, Out-1-2.
“I didn't know.” He hadn't known for sure.
Stiles raises his gaze to meet Derek's own, honey brown eyes resigned but not betrayed.
“I'm sorry,” and he supposes he should be grateful that Stiles couldn't pick up the tick in his heartbeat that would give him away just yet. “I know this isn't what you wanted.”
Brown eyes flicker to gold, stay that way for a breathtaking five seconds. He knows his boy is smart. That once he comes into himself, once he can pick up all the tells, he'll be unstoppable. Derek will have to get into the practice of skirting around the truth, or just doling out half truths, if he wants to hide things from him. He puts a hand on Stiles' shoulder and is gratified by the way he leans into the touch. He sits beside him and takes his chances, draws the boy into a hug that he practically melts into.
He catches that scent again, the one that screams of pack, of mineminemine, and he realizes that Stiles has already chosen him. He hides his smile in the teen's hair, strokes a soothing hand down his back.
“I'll take care of you,” Derek promises. Stiles is his now. He won't let anyone take something this important away from him again. He knows better now.