In hindsight, Stiles’ sensitivity to even something so tame as being touched should’ve been obvious.
The kid’s always shown an affinity for physical contact - he’s always been the first to initiate hugs or suggest pack cuddles, and he‘s always greeted his dad and all of his friends with high fives, hugs, shoulder bumps.
It’s pretty obvious that Stiles has always been an affectionate person. Even in the months after the Nogitsune, when he grew quieter and more conservative with his touches, it was obvious he still craved the comfort of physical contact, reaching out automatically before drawing back, unusually fearful of rejection.
So Derek knew Stiles liked being touched; he just hadn’t been prepared for how much.
The first time Derek finds out just how sensitive Stiles is, it’s unintentional. Or, unplanned, to be more accurate.
It’s early summer, and the pack has collected again after their first year at college. Most of them had stayed close, gone to community colleges or colleges in nearby towns; close enough for weekend trips home, or within range for Derek to not feel the tug of pack bonds being stretched too far from the territory.
Except for Lydia and Stiles, who had strayed a little further, to UCLA and Berkeley respectively. Of course, Jackson had trailed after Lydia, and they’d made trips back home frequently: every full moon, Thanksgiving, winter break, birthdays, spring break.
Stiles, on the other hand, hasn’t been back in Beacon Hills since winter break, and the distance has obviously affected them all.
He spends his first day home catching up with his dad, naturally. Scott and Mellissa force him and the Sheriff over for dinner his second night home, and then Isaac and Erica demand his undivided attention for his third day back.
The fourth day, Derek has grown irritated by the pack scent having become faint on Stiles, and coerces him into a not-gentle scentmarking session - he’ll let the pack pile him into a cuddle puddle later to reinforce it, but right now he needs Stiles drenched in his scent. His scent’s the strongest, carries all of their scents - and even if Stiles isn’t a wolf, Derek is still his Alpha. Strictly from a logical standpoint, it just makes sense for Derek to be the first to remark the pack’s claim on the boy.
Stiles has barely gotten through the pack house door before Derek has him crowded up against it, a little too eager to refresh the smell of pack and family and home. Stiles doesn’t complain, just as eager for the reminder of pack belonging, but he does herd Derek over to the couch, because being pressed into a doorknob by a 200lb brick-bodied werewolf isn’t the most comfortable.
Even having grown up a wolf in a family of wolves who didn’t care about human things like personal space or boundaries, he generally tries to take these things into consideration around human pack members who might not typically enjoy being crushed and/or mauled - but he can’t find the energy to try to control that urge when his pack member hasn’t smelled like his in six months. So he immediately pulls Stiles down to straddle his thighs, desperate to be as close as possible, desperate to cover him in pack smell, and Stiles moves willingly, settling close against him.
“You smell like strangers,” Derek complains, huffing.
“I know, big guy,” Stiles replies, sighing, one hand on the back of Derek’s head to urge his face into his neck. “But you have three whole months of me before fall semester. Plenty of time to rub pack smell all over me.”
“Not good enough,” Derek says, “You have to come back home more often.”
Stiles laughs; probably a little at Derek’s blatant desperation, and a little at the fact that Derek’s nose is tickling him where it’s dragging lightly down his neck. “Not all of us can afford gas money for a six-hour round trip drive every weekend, Derek. Do you know how much gas the jeep eats?”
Derek whines. “I don’t know how many times I have to tell you, Stiles, I can give you the money - just come back. Every month, at least. We need you here.”
Stiles sighs and slumps against him; they’ve had this conversation a dozen times. He has a part-time job, and the money’s not great but it’s enough for him to survive, as long as his jeep doesn’t need repairs, and as long as he doesn’t order takeout, or travel off-campus too often.
“You have me for three months, right now, Derek. I’ll figure something out, okay. Just keep doing your possessive sniffy thing and we’ll worry about that later.”
Derek does, happily. He’s not careful about it like he would be usually, or like he is with the rest of the pack; he shoves his face into Stiles’ throat, rubbing his scruff against Stiles’ soft skin, and Stiles lets him do it without making noise about the scratchiness or the aggressive redness he’ll be sporting later.
Stiles relaxes into it, goes limp against him, lets Derek tilt his head this way or that to look for unmarked flesh. But then when Derek starts laying teasing nips and bites along his neck and shoulder, he lets out a quiet noise of surprise - Derek doesn’t usually bite during scentmarking, but it’s been months, and open-mouthed presses work the scent in deeper and longer than just skin-to-skin.
“Sorry,” Derek says, though he doesn’t sound sorry at all.
“I’m not complaining, just - my neck is sensitive, so careful with the teeth, okay?”
“If you came back home more often,” Derek grumbles, “I wouldn’t have to be so aggressive about it.”
Stiles rolls his eyes, and even though Derek can’t see his face where it’s pressed into the side of Derek’s neck, he’s sure he can feel the eyeroll. “Point taken. I’m just saying, don’t get carried away with the chewing.”
Derek’s fingers around his chin tighten, and then there’s the distinct feeling of fang-sharp teeth pressing into the hinge of his jaw, anything but gentle. The noise Stiles lets out can’t be mistaken for anything other than what it is - a breathy gasp. His fingers flex and clench in the hair at the nape of Derek’s neck, and Derek feels the shudder running through Stiles’ body against his.
“I’m serious, Derek. Like really sensitive,” Stiles says, a little muffled by where he’s shoving his face into Derek’s shirt.
Derek grunts, lathes his tongue over the spot he’s just bitten. He expects Stiles to relax again, but it seems to have the opposite effect; Stiles shivers again, jerks a little forward and then jolts back, like he’s not sure if he wants to crawl closer to Derek or pull away completely. Derek solves that for him by tightening the hand on his waist, preventing him from moving back.
“Maybe,” Stiles says, voice shakier than it had been a second ago, “maybe just the nose thing, yeah? I-“
Derek growls, drags his nose up Stiles’ jaw to just below his ear and nips.
“Derek,” Stiles breathes out, and that - that was definitely a moan.
Derek’s asshole days are over - for the most part - but he can’t deny that he’s still a little vicious, especially when it comes to marking what’s his, and especially when it produces results like that. So he does it again, a little harder.
Stiles’ response is...satisfying. His fingers twitch in his hair again and his hips jump forward just slightly, just enough that Derek comes to the shocking realization that when Stiles’ had said his neck was sensitive, he’d been trying to tell Derek that it was apparently a fucking erogenous zone for him, and. Derek can’t exactly be expected not to take advantage of that, not with Stiles squirming - closer, not away - in his lap.
And especially not when Derek takes a long, deep, not-subtle sniff, right where his nose is tucked into that spot behind Stiles’ ear, and all he can smell is sex, heady and dark and syrupy sweet.
He pulls his mouth away from Stiles’ skin - to a very gratifying whine of disappointment - and tips Stiles’ head up to get a look at his face.
Which is nothing less than a picture of absolute bliss; eyes closed, lips parted, cheeks flushed - Derek groans at the sight of him.
“Jesus,” he grunts, “you weren’t lying, huh?”
Stiles opens his eyes, blinks at him - and if Derek had had any doubts of the affect he’s been having on Stiles, he doesn’t anymore. Stiles’ eyes are the definition of bedroom eyes, glassy, pupils dilated, lids half-lowered so his gaze is directed under long eyelashes.
“Derek,” Stiles says again, breathless and a little weak, and it sounds just as desperate as Derek feels.
Derek’s wolf salivates, and he can’t hold back the shiver that goes down his own spine; the boy is heart-stoppingly beautiful like this. He’d always thought he was cute in a quirky, unique way, but even moreso now, a little shy and shaking apart in Derek’s arms, under just the press of his mouth against his skin. An Alpha’s fucking wet dream, basically.
He feels absolutely no shame at all about his sudden desire to make Stiles come, just like this, in Derek’s lap and still fully dressed, with reverent cries of Derek’s name on his lips. He’s already addicted to the sound of his sweet little moans, the tentative movements of his hips. Derek wants to fucking break him.
“Stiles,” he says, his own voice a good octave lower than its usual timbre, “Are you - can I?”
It’s not even a whole question, and he’s not sure what he was trying to even ask, because he wants everything, but Stiles doesn’t seem to care, just as gone on pleasure as he is; he nods, frantic, rolls his hips down unconsciously. Derek wonders, briefly, if Stiles can feel the bulge in his own pants where he’s pressed against his crotch.
Not that it matters; Stiles’ approval throws him into action again, and Derek doesn’t hesitate for a second further before he gets his hands on the hem of Stiles’ shirt and practically rips it off, already drooling at the thought of more skin to mark up under his hands, already eager to find out if Stiles is as sensitive everywhere else.
The first thing he does when faced with the new span of skin is press his face right in the hollow of Stiles’ throat, between his collarbones. He smells incredible there, like clean sweat and pure Stiles, lemon and sage, and Derek can’t help but flick his tongue out and lick a long line up his throat.
Stiles’ head tips back with a punched-out moan, and Derek responds with a growl and a firm bite right over his pulse point.
“Can’t get enough of your fucking sounds,” he groans, following up the bite with a wet, open-mouthed kiss. Now that he’s gotten Stiles’ permission to continue, he’s kind of stuck on the idea of marking him with something a little more visible than scent; something that even humans would be able to see. “I’m keeping you. Forever.”
“Should’ve known you’d be the possessive type,” Stiles mutters, but he doesn’t jerk back or scramble out of Derek’s lap, so Derek’s pretty sure he doesn’t mind at all.
He drags his hands up Stiles’ sides, resting right on either side of his chest, teasingly close to his nipples, and if the way Stiles’ grinds down and whines is any indication, Derek was right to think he’d be sensitive there too.
“Fuck,” Derek says, “so gorgeous. Can you come like this?”
Stiles hips’ grind into his again, a little harder this time, and yeah, Derek thinks, Stiles is totally going to come just like this.
“Probably,” Stiles huffs, “keep going and we’ll find out.”
Derek growls again, reins in his fangs to land a vicious bite just above Stiles’ collarbone, absolutely delights in the way Stiles body goes tight, probably already close. He smells close - Derek can smell his pre-come dripping into his jeans; if he could bother to tear his face away from Stiles’ skin and look down, he’d probably see the wet patch forming.
He licks over the spot he’s just bitten, sucks a bruising kiss there, and then inches his right thumb closer to Stiles’ nipple. Doesn’t touch it yet, but Stiles squirms, clearly trying to get Derek’s thumb closer.
He keeps going, keeps biting and sucking and licking at Stiles’ neck and throat and collar like a fucking chew toy, until Stiles’ moans turn high and needy and he starts whining and whimpering, and then he finally presses his thumb to Stiles’ nipple. Just tentatively, just a brush, but Stiles’ hips hump forward and he cries out, so Derek presses harder just as he lands a particularly harsh bite to the meat of his shoulder-
He smells it just before it happens. Stiles’ hips jerk forward twice and then he stills, soiling his pants, Derek’s name broken on his tongue, and he practically collapses against Derek, shivers of aftershocks rolling through his body.
Derek gentles him through it, as gentle as he can be with the urge to keep Stiles like this forever, and with his own dick obscenely hard against the zipper of his jeans. He pets down Stiles’ sides, turns his bites into softer kisses against the blossoming bruises.
It’s a few minutes before Stiles gets his brain back online, gazes up at him doe-eyed and fucked-out.
“Oh my god,” he says, and he has this deliriously happy grin stretching across his face. “Told you I was really sensitive.”
“Yeah,” Derek agrees, already planning on spending the next three months exploring Stiles’ erogenous zones, “Where else are you sensitive?”
Stiles hides his face back in Derek’s neck and groans. “You’re gonna ruin me, aren’t you?”
Derek presses his palm against Stiles’ lower back, soft but firm. Possessive. “Meant it when I said I was keeping you forever.”