The only reason Derek's at the Halloween party is because they're only two nights off the full moon and his pack has a tendency carry what Stiles calls 'Full Moon Dickery' (Derek can hear the capital letters) for days after. Derek thinks it might be a bitten werewolf issue because his family never had this ridiculous problem.
He hadn't intended to come but Stiles' constant complaints that he wouldn't be able to enjoy himself because he'd be worrying about Scott attacking someone, probably the newly returned Jackson, or seeing more of Boyd and Erica than he'd ever needed to see had got to him. He's looking for Stiles now, to tell him he can go and drink as much as he wants and hook up with whoever he wants, because Stiles hasn't been answering his phone.
Derek can smell him, faintly, in the press of people filling Lydia's house and yard. That familiar mix of near-constant teenage arousal, the sharp spike of his meds and the honest Stiles smell that grounds it all. A girl wearing a barely there “sexy” witch costume bounces off of Derek and he stops himself from scowling at her when she stares wide-eyed up at him.
“Hey,” he says, drawing her eyes away from his chest. “Have you seen Stiles?”
Her face contorts into an obvious pout as she twirls a strand of purple wig hair around her finger.
“He's around,” she says, waving her other hand behind her. “Dancing. But you should come hang out with me, I'll -”
Derek moves away before she can finish her sentence, not interested in the come on, and slides into the dancers. Stiles' scent is stronger here and Derek manages to avoid most of the gropes sent his way as he tracks it. Stiles is right in the centre of attention, he's not surprised by it – though he's a little surprised Stiles is dancing at all given how often he's said he has to be drunk to do it. Derek frowns but he can't smell any alcohol mixed in with Stiles' scent.
The dancers part and shift around him and Stiles' scent fills his nose, blocking everything else out, and it's a little like being high, the way it rushes to his head. He blinks and turns his head to his left and there's Stiles' back, dancing with some girl Derek doesn't recognise. Stiles isn't wearing a costume that Derek can see but he's not really thinking about that right now. He's thinking about the sinuous way Stiles is moving, the curves and shifts of his body, and the unfortunate way that it's licking fire up his spine.
The girl catches sight of Derek and Derek knows he's staring but he can't stop. She leans up to Stiles' ear and whispers something Derek can't focus on and then points to him. Derek's trying to back up even as Stiles turns and Stiles is wearing something – he's wearing a mask. It looks old and beautiful and covers the top half of his face, leaving his mouth free, and seeing the barest hints of Stiles' eyes behind it makes Derek shiver.
Stiles tilts his head, the movement curiously bird-like, and then he's taking the few steps necessary to reach Derek. The girl lets out an aggrieved huff and gets absorbed back into the dancers. Derek wants to back the hell away from this Stiles who moves with such precision and grace but it's like he's pinned to the spot. Captivated.
Stiles reaches him and then takes a final half-step to put himself right inside Derek's personal space. Derek's breath catches in his chest, completely wrong-footed by the reversal, and Stiles' mouth curves into a sly smile. The mask up close is a shimmering blue-black colour, with delicate patterns drawn on it that Derek can't make out – they seem to shift in the light. Stiles puts one hand on the back of Derek's neck and slides the other around his waist, under his leather jacket. Derek feels sweat prickle between his shoulder blades as heat radiates outwards from Stiles' touch. Stiles leans in so his mouth is next to Derek's ear, warm breath making the flesh tingle.
“Dance with me,” he says, each word said so precisely that it can't be anything other than a command.
Derek doesn't dance, not really, because he's never really had to. He lets Stiles pull him into a dance that feels a little dirty and is too slow for the music. Derek knows how to use his body, knows he's moves with grace, but he's got nothing on this Stiles. He tries to follow Stiles' movements, he's a decent mimic, but he can't match the silky, sinuous twists and slides. He lets his head fall forwards, his forehead resting against the top of the mask and their noses occasionally brushing together, lets Stiles guide him.
It's hot, stifling, but Derek knows it isn't really – it's fall and his breath would probably mist if he was outside – it's just Stiles that's making him feel like this. Right in this moment he can't remember why Stiles isn't supposed to make him feel like this. Not with Stiles a warm length leaning up against him, moving him to some beat inside his own head, his hands scorching into Derek's back.
Derek's not sure he can remember what he was trying to achieve here.
“That's not really a costume,” Stiles' voice returns, curling into Derek's ear. Derek suppresses a shiver.
“It's a costume,” he says, shocked by how rough his voice sounds. He needs to get out of here.
“It's what you wear every day,” Stiles says, his fingers digging into Derek's neck for a moment.
“It's -” Derek stops when he feels Stiles' lips press briefly to the hinge of his jaw. “Happy Days.”
“I need more than that,” Stiles says, his voice sly as the hand on Derek's waist inches under his shirt.
“The Fonz?” Derek doesn't mean for it to be a question but that's how it sounds, forced out of him by the press of Stiles' hot fingers to the small of his back.
“The rebellious loner with all the chicks following him around?” Stiles says, his mouth still too close. Too close. “I can see that.”
“It's not really a costume,” Derek admits, feeling awkward in a way he can't remember ever feeling before. His heart is pounding in his chest, drowning out the steady rhythm of Stiles' heartbeat in his ears, and he feels a little like he can't breathe.
He thinks this might be the way Stiles feels most of the time. It's not really pleasant.
“I don't really care,” Stiles says, fitting their hips together and rolling against him. Stiles is hard and, more importantly, so is Derek and he should stop this now, no matter how much he wants it, because – because -
Because is hard to find when Stiles is pressing little kisses to Derek's neck, all the while manoeuvring them toward the edge of the crowd.
“If you want me to stop,” Stiles says, pausing over Derek's jumping pulse point. “I'll stop.”
Derek never wants him to stop and he shouldn't want that, not when Stiles is still not quite eighteen and his father's the Sheriff and Derek is responsible for his safety more often than he'd like to be (but not as often as his traitorous body wants). Derek lets out a low breath.
“Don't stop,” he says, bending his head to mouth at the column of Stiles' neck. Stiles tastes of Stiles and sweat and something sweet and something dark. It's heady.
Stiles pulls back, that sly smile still on his mouth, and reaches down for Derek's hand, leading him away and out. It's raining now, heavily, so everyone else has crowded into the house and the yard is empty and quiet. Derek checks anyway, using his ears because all he can smell is Stiles, and they're alone.
Stiles, this fey and quicksilver Stiles, presses Derek back against a wall out of sight of the party. They have shelter from the rain but the air is still cool against Derek's over-heated body. Stiles leans up against him again and kisses Derek, an explosion of heat and wet and Stiles knocking Derek's brain offline for a long moment before he's kissing back. He lets Stiles feel how much he wants him in the kiss, how much he's been holding back, and Stiles lets out a breathy moan that makes Derek's cock twitch in his jeans.
“Jesus,” Stiles says when he pulls back, a hint of the regular Stiles and that balances Derek out. Brings him back. Stiles drags a thumb over Derek's bottom lip, eyes tracking its progress, and Derek lets himself touch Stiles at last, dragging his hands down Stiles' sides to settle on his waist. Stiles rolls against him, instinctively, and Derek spreads his legs a little so Stiles can fit between them perfectly.
Derek would swear he's never thought of this if you ask him. He'd also hope you weren't a werewolf and therefore wouldn't hear the lie of it. Holding Stiles against him, rocking into the forward motion of Stiles' hips, and Stiles' mouth hot on his throat, making marks that will be gone in moments. Of course Derek's thought about it.
“I want,” Derek sucks in a breath, squeezes Stiles' hips. “I want to see your face – can I see?”
Stiles looks at him, his first moment of hesitation since he saw Derek, and Derek holds his breath. Stiles takes his hands slowly from under Derek's shirt, where he'd been tracing patterns into his back, and pulls the mask off carefully, exposing the eyes that Derek will never admit to seeing in his dreams. He leans away from Derek and puts it down on a nearby table. When he looks at Derek again there's a nervousness that wasn't there before but Derek doesn't mind because that's just Stiles.
He moves his hands and cups Stiles' face, looking into his eyes to be sure, and can see Stiles' resolve harden, feel the way Stiles finds the confidence again, even unmasked. Derek can't stop the smallest of smiles creasing his face and Stiles' hand comes up instantly to trace it with a finger.
“Was beginning to think you couldn't do that,” Stiles says, leaning in to replace his finger with his mouth. The kiss is sweet and pointed, finished with a flash of Stiles' tongue that leaves Derek wanting more.
“What?” Derek asks, brushing his thumbs over Stiles' cheeks and feeling the flushed heat there.
“Smile like you mean it,” Stiles says and this time Derek kisses him, licking into Stiles' mouth and swallowing the meaning of his words.
Stiles pulls away and drops to his knees, hands steady as they unbuckle Derek's belt. Derek makes a cut-off sound and catches Stiles' hands, shaking his head.
“You don't have to -” Derek starts but Stiles pulls away from his grasp and goes back to the belt.
“I want to,” Stiles says, his voice humming with the want and his heartbeat fast but steady in his chest. Derek lets out a shaky breath and tilts his head back against the wall.
Stiles makes short work of his jeans and then makes a delighted noise when he sees that Derek's not wearing any underwear. He runs his hands up and down Derek's thighs until Derek looks down at him again. Then he smiles, slow and sly, and leans forward to lick a stripe up Derek's cock where it's curving against his stomach.
“Fuck,” Derek breathes out. Stiles' eyes spark up at him and then he's taking Derek's cock in one hand and sliding his mouth over the head.
Derek's hips rock forward once and Stiles makes a noise and presses him back with his free hand. Stiles knows that's not enough to stop Derek if he wants to move but Derek obeys the touch, letting Stiles have control. Stiles hums in approval and Derek's hands find their way to Stiles' shoulders of their own volition, gripping just shy of too tight.
Stiles' mouth is hot and sinful and it's one thing knowing intellectually that Stiles has been having sex over the past year and another receiving first hand the fruits of that exploration. Stiles is good at this and Derek feels a flash of jealousy toward whoever got to experience Stiles learning this. Stiles' cheeks hollow as he sucks, his hand moving up to meet his mouth as his head bobs in a steady rhythm, and Derek loses himself in the feel of it.
Stiles' eyes flutter open as he pulls off to trace a teasing line down the underside of Derek's cock. Derek's breath comes in short pants as Stiles moves to his balls, sucking and kissing tenderly, his hand always stroking, thumb sliding over the slick head of Derek's cock.
“Fuck,” Derek says, bringing a hand up to cup Stiles' neck and squeeze. “Stiles. Fuck.”
“So eloquent,” Stiles says, his voice hoarse. He looks up at Derek, meets his eyes as he slides down Derek's cock again, not stopping until it hits the back of his throat. The strain of not thrusting forward is enough to make Derek's legs shake.
Derek grabs the hand Stiles has pressed against his hip and links their fingers together. Stiles' eyes widen slightly but he squeezes Derek's hand back, lets Derek have the contact. Stiles pulls back to lavish attention to the head of Derek's cock, hand stroking faster and hard along the length, and Derek can't stop the little noises that flood out of his mouth. He feels himself curving away from the wall, his body desperate for climax, and forces himself to lean back, to hold still.
Stiles reads his need and changes rhythm and tempo, tongue curling in a way Derek would've thought impossible, his hand strong and sure and Derek – Derek needs this, wants it so bad, his balls tightening and his whole body going rigid as Stiles sucks and slides down, taking his cock almost all the way in.
“Stiles – I -” he manages before he comes and Stiles swallows and swallows, drawing Derek's orgasm out of him with each slick pull of his throat and Derek's head hits the wall so hard that if he was human he probably would've broken something.
Stiles pulls off with a pop, his hand gentling Derek through the last few aftershocks, and leans his head against Derek's thigh. He smiles up at Derek and this one is smaller and more privately pleased than anything else. Derek presses a thumb to that red mouth and Stiles licks the tip with a dart of his pink tongue.
Derek makes a noise, something garbled from the back of his throat, and tugs Stiles up to kiss, tasting himself on Stiles' lips and that's perfect. So perfect. Stiles groans and grinds himself against Derek's leg, drawing Derek's focus to where Stiles is still hard. He gets Stiles' belt and jeans undone one handed - can't bring himself to take his hand away from Stiles' neck where he feels the fluttering heartbeat he can hear in any crowd.
Derek takes a moment away from Stiles' mouth to lick at his hand before pulling Stiles' cock out of his boxers. He sucks a mark low down on Stiles' neck as he gets his hand on Stiles' cock, hard and hot and silken in his hand.
“Just so you know,” Stiles says as he thrusts into Derek's grip. “Normally I last longer than I'm gonna – that was just too fucking hot for me to not -”
He stops and moans when Derek presses a thumb just under the head of his cock. Stiles' hands flail wide for a moment and then come to rest on Derek's hips, flexing and gripping as Derek strokes him. Derek can smell Stiles' arousal, hears the double-time beating of his heart and feels Stiles' body tensing in increments. Stiles finds his mouth again and Derek kisses him wet and dirty. Stiles' breath hitches and his hips jerk forward and then he's shaking through his orgasm, his come spilling over Derek's hand.
Stiles sags against him after he comes, his thumbs rubbing slow circles against Derek's hips, and Derek's suddenly very aware that his jeans are still around his knees. He licks Stiles' come off his hand and Stiles makes a groaning noise and turns his head away from the sight.
“You should be illegal,” Stiles mumbles against Derek's jacket and Derek surprises himself by laughing. Stiles pinches him in retaliation and Derek pushes him away, gently.
Derek pulls his jeans up while Stiles tucks himself away with shaking hands. They lean against the wall, shoulders pressed together, and Derek listens to Stiles' breath slowing, his heartbeat returning to its familiar slightly-fast rhythm.
“So,” Stiles says quietly, turning his head toward Derek. “That was a thing that happened.”
“It was,” Derek agrees. He's waiting for the guilt – the guilt he always feels after sex – but it's just not there. He feels calm, calmer than he has for a long time.
“I'm sort of hoping that wasn't just the last leftover full moon stuff,” Stiles says and Derek looks at him from the corner of his eye.
“I don't really have the same problems they do,” he says, shrugging.
“I've noticed that,” Stiles says, nodding to himself. “I notice things like that. I just – I'm trying to figure out why that just happened.”
“Because you weren't afraid to take a chance,” Derek says and knows as he says it that it's as much for him as it is for Stiles. From the soft noise of assent Stiles makes he thinks Stiles knows that too.
“Why did you ask me to take the mask off?” Stiles asks, reaching out to pick it up.
“Wanted to know it was you,” Derek says with another shrug. Stiles cuts his eyes toward him.
“It freaked you out?” Stiles asks, holding the mask up to cover his face for a moment. Derek looks away.
“It's not that,” he says, though it is a little. “I just wanted to see the Stiles I know.”
Stiles is quiet for a long time and then he shifts in front of Derek, draping himself against him again. Derek's arm goes easily around Stiles' waist and they fit together so nicely, so neatly, that he almost thinks it's by design.
“When I was a kid Mom used to take me to this drama thing,” Stiles says, leaning his head against Derek's shoulder. “It was supposed to help me with all the energy I had – this was before the diagnosis. I guess it did, sometimes, but most of the time I was no different. Then the person who ran it, Miss Kate we called her, did an afternoon where she made us all wear masks and I -”
“You were different,” Derek says, reaching out to touch the mask. Stiles nods.
“It's weird, putting on a mask,” Stiles says, briefly holding the mask over Derek's face and looking at him. “It's like magic but not. They've got power in them. I used to lose myself when we did the mask stuff – I could just be for once, my brain would shut down and it was...peaceful. I don't like to do it a lot, now, because I need to be on all the time. But tonight. You know.”
“It's Halloween,” Derek says, taking the mask from Stiles and helping him fit it back over his head. He runs his fingers along the edges of the mask, where it ends and Stiles begins, then leans in for a brief kiss.
“Do you like me like this?” Stiles asks, the slight shift in tone speaking to the way the mask affects him.
“I like you however I can have you,” Derek says, because Stiles in the mask makes him feel brave too.
“Big words,” Stiles says quietly, his tongue touching briefly to his bottom lip.
“I mean them,” Derek says, watching Stiles. Stiles watches him back, thin slivers of his eyes visible behind the mask.
“Why now?” he asks, tilting his head.
“Why not?” Derek asks back, raising an eyebrow.
“I'm not exactly -” Stiles stops. There's a lot of ways he can finish that but Derek has the right answer to all of them.
“I know,” he says, pulling Stiles close for a moment. “You wear another mask under this one and another one under that. All the way down to the Stiles underneath. I'm interested every one of them. If you'll let me be.”
Stiles stares at him for a long time and Derek can almost hear him thinking it through, picking it apart and trying to get to the heart of Derek's meaning. Derek lets him stare, even though the scrutiny is uncomfortable, and lets out something like a sigh when Stiles nods and presses a brief kiss to his lips.
“Come on,” Stiles says, linking their hands together and pulling Derek away from the wall. “Better make sure the kids aren't getting into trouble.”
Derek lets Stiles lead him back into the party, not caring that the pack will be able to smell them all over each other. He gets to have this Stiles, and maybe all the Stileses eventually, and he feels free because of it.