Derek really should know better.
It's the full moon and the wolf is right under his skin, clawing for the shift and the run and the chase. Derek already ran, though, with the others, howling and frolicking, and indulging in all the baser instincts that call out to every shifter during their power phases. But it obviously wasn't enough, because something made him turn over for Stiles in bed, after, even though he could have chosen literally any other position, and Stiles would just as gladly have gone along with it.
And it's not like they haven't done it like this before, but during the full moon? Derek should have been more conscious of the signals he's sending his animal side. But it's too late, far too late, and Derek already feels his orgasm tickling at his insides every time Stiles bottoms out with a filthy grunt of exertion and pleasure. The hands pulling at his hips are slick with sweat, and Stiles curses when he loses his grip again, choosing instead to lean over Derek, bracing himself on either side of his head. Derek moans into the mattress, because the angle is perfect now, so perfect, and his eyes scrunch closed in anticipation of his climax, the wave so close to cresting he can almost taste it.
Stiles is struggling, though, not bolstered by the moon, and therefore no stronger and no more flexible than any other time, and in his attempt to regain momentum as he tires, he braces himself on Derek's back, just briefly, pushing him down, and something sparks.
Derek can feel the red burn in his eyes, and his claws slice out so fast his fingertips throb. But it's not aggression, and there's no urge to fight. On the contrary.
“Fuck, alpha!” he whines, the words slurred by his fangs. Any hope Derek had that Stiles might not have heard is dashed when Stiles stops dead, panting hard.
“Never mind, keep going. Come on,” Derek snaps, even though he can already feel his dick go soft from mortification. He tries pushing back against Stiles, but is met with firm hands, stilling him. Stiles is obviously silently freaking out, and Derek sighs in resignation as they pull apart.
He starts moving to leave the bed and clean up, but Stiles pulls at him insistently until Derek is on his back, and Stiles is seeking out his still red eyes. Derek lets him look, lets him take in the eyes and the claw marks in the mattress and the fangs... and there's a surprising calm on Stiles' face. But there's also question there, and Derek feels like squirming under the scrutiny until, finally, Stiles puts an end to it by leaning in for a kiss, easing in to lie comfortable between Derek's legs. The kiss is slow, and mostly one-sided because of the fangs, but Stiles never lets details like that distract him from his goals, and it's normally a comfort to Derek, but right now it only reminds him of his embarrassment.
“You're so good,” Stiles murmurs against his lips. “So good for me, Derek. Always so good.”
Derek isn't sure where this is coming from, but it makes him relax a little, because if Stiles isn't freaking out they could possibly still pick up where they left off.
Stiles noses at him, under his chin, up along his jaw, and Derek tilts his head instinctively from the wolfish gesture. There's a small gasp, which sounds like a whoosh of air so close to his ear, and Stiles' pulse picks up. It's followed by a tense few seconds where Derek is half sure he fucked up again, but then...
“So good for your alpha. Aren't you, beta.” Stiles whispers in his ear, and Derek tenses, his cock jumping against his stomach so hard that Stiles definitely feels it too, and braces himself for the worst. Mocking, probably. But Stiles just moves away enough for their eyes to meet again, and there's no mocking there. None.
“Aren't you?” he prompts again, and Derek's mouth goes dry.
“You are, aren't you,” Stiles agrees, his smile strangely tender, and he reaches up to brush his knuckles gently across Derek's temple. “Always so good for your alpha.”
Derek's instincts are going haywire, because as an alpha his instinct should be to assert his dominance. Not in the sexual sense, necessarily, but he should at least feel the challenge. Instead, all he feels is a rush of pleasure.
Maybe it's because Stiles is human. Or maybe it's because Derek was never meant to be an alpha. It was always meant to be Laura. Derek was born a beta, and had expected to be a beta for the rest of his life. So maybe it's just something ingrained. Whatever it is it makes him breathe harder, and Stiles smiles so lovingly at him it almost hurts to look at.
“Yes, alpha,” Derek whispers, feeling like he should be punished for it somehow, but Stiles just kisses him again.
“Such a good beta only deserves the best,” Stiles murmurs, rolling his hips against Derek's cock as it hardens again. “I'm gonna take such good care of you, Derek. My sweet beta. Are you gonna let your alpha take care of you?”
“Yeah. Yeah.” Derek's voice is barely a whisper, it feels so illicit. But Stiles rewards every little acknowledgment of the reversed dynamic with another roll of his hips, eventually followed by his slender fingers, closing around them both.
“Does that feel good, beta? Do you like my hand on you?”
“I wanna give you everything,” Stiles says breathlessly, his own pulse racing again to match Derek's. “Everything, beta. You hear me?”
“And you deserve it. All of it. Because you're so good for me. So good for your alpha.”
Derek whimpers, and reaches for Stiles. But he's stopped by a gentle grip on his wrist, leading his hand over his head.
“Keep those claws up there, beta,” Stiles orders softly, and only then does Derek realize that he's still shifted. “Both of them. Can you do that for me?”
He brings his other arm up without hesitation, curling both hands around one of the horizontal slats in the headboard, and tilts his head back again, as if he wasn't already showing his soft parts as blatantly as possible.
“That's good, Derek. Perfect. So perfect for me,” Stiles sighs, and moves his hand faster. “Gonna make it so good for you.”
Derek keens, and shudders from the amazing friction on his cock. But it's not enough, somehow. It's not what he wants, and realizing it is like release in itself.
“No, wait,” he says, and Stiles lets go of him immediately.
Derek pulls away just enough to turn over, and get back on his knees, face flushing from the tiny gasp behind him when he presents, opening up to Stiles' gaze and his cock. “No, like this,” he explains, but he obviously doesn't need to, because Stiles is on him before he even has the words out.
“So that's how you want it, huh? Wanna bend over for your alpha? Wanna be fucked full like a bitch?”
Stiles' words lance through Derek like electric shocks, and he whines, low in his throat, and arches his back more. “Yes, alpha, please.”
The sound Stiles makes is not quite a growl. He can't make the right movements in his throat. But it's close. Close enough that Derek responds to it, and tilts his head down and to the side on reflex, opening up for a bite. It's never been like this for him, ever.
But Stiles takes it in stride, sliding his hands up Derek's back until he can push down again, pressing Derek's shoulders into the mattress.
“Such a good boy for me, beta. And good betas get what they want. What they need.” His cock is nudging at Derek's hole, and it's a shivering kind of ache just how much Derek needs it to fill him up.
“Yes. Need you, alpha. Need you to fuck me.”
The long push as Stiles thrusts back inside is like a slow balm on places Derek didn't even know were raw, and he keens long and high-pitched, until Stiles is finally all the way in. Where he belongs.
“That's my beautiful bitch,” Stiles rumbles, his naturally deep voice going deeper still, and Derek is feeling crazy with it. “Come on, beta, work for it.” The words are followed up by a small slap on Derek's ass, and he jerks, having completely forgotten for a second that Stiles is actually not an alpha, powerful beyond measure with endless stamina.
But it doesn't actually change anything, because his alpha just gave him an order, and Derek is helpless against it, hips starting to move before he even realizes it. Stiles' hands keep him grounded, weight heavy on his back, like a perfect anchor, and Derek can't move much, but it's enough, it's almost perfect, and he shakes with every roll of his hips.
“Alpha... alpha,” he pants, claws digging into the headboard slats, ready to fly apart, the edge teasing at him again already, so close and yet so far.
“Yeah,” Stiles moans. “That's it. That's a good boy.”
“Such a good beta. So good for me-”
As if called by it, Stiles immediately starts meeting Derek's movements with thrusts of his own, clashing them together in stabs of pleasure that make Derek's damn spine rattle. He wails through his fangs, and hides his head under his arm, feeling weirdly like he shouldn't be making so much noise, and at the same time baring the back of his neck again, wordlessly asking for something Stiles can't truly give.
But Stiles definitely doesn't care about what anyone thinks he can or can't do, and one brutal thrust later he crashes down on top of Derek with his full weight, and sinks his blunt, human teeth deeply into the skin on Derek's nape, yanking at that primitive thing deep inside him. It's like cracking open a pressurized container, and everything rushes out of Derek in a blinding roar, leaving him sinking into blackness.
He comes to slowly, blinking wetness out of his eyes, and feeling somewhat sheepish. But good. Holy fuck, does he feel good.
“That... that was...” he trails off, completely lost on how to explain anything of what just happened.
Stiles is still gasping for breath against his spine, and lets out a weak laugh. “That was freakin' awesome, that's what. Holy shit, please tell me we can do that again?”
“I... don't know if I can,” Derek admits, because he didn't even know it was possible in the first place.
A few more wheezing breaths later, Stiles manages to lift his head. “Would you like to?”
“...yes.” Because he does. Instincts or pack mechanics be damned, he hasn't felt this good in years. Possibly ever.
“Then no biggie,” Stiles sighs, and licks across the slowly healing bite, making a shiver run down Derek's spine. “We'll do it again if the mood strikes. If not, it's not like our usual stuff is boring or anything.”
Derek is not sure it's that simple, but he nods, wanting to hope for the best, for once. Stiles seems to bring that out in him, which is weird considering they're usually both brutal cynics.
“I'll be your alpha anytime,” Stiles slurs, and starts snoring, and Derek feels like maybe this time two negatives can in fact make a positive.