They’d been sleeping together for about four months when it happened.
Okay, not like Stiles had been counting or anything, but...well, he’d been counting. It’d been three months, twenty-five days, and an assorted number of hours that might be ticking to a close if the fury boiling off Derek’s shifted skin had anything to say about it.
Sometimes, see, Stiles had an idea, and it seemed fantastic at the time, but he didn’t stop to think about what might happen after his fantastic idea had been carried out. Which was why he was locked in the bathroom with a fur-clogged razor in his hand while Derek pounded an angry fist on the other side of the door.
Stiles slid to the floor, and after another loud thump and a world-weary sigh, Derek audibly did the same.
“Just open the door,” Derek said, his voice muffled enough that Stiles figured he probably had his face pressed against the wood. Stiles hadn’t actually flipped the lock into place, and they both knew it. It wasn’t like any of the house’s flimsy doors would hold up against a werewolf who actually wanted to get through, but Derek didn’t use his strength for that kind of thing. He pulled back, constantly. Kept his distance when he could tell Stiles wanted some space. Respected the sanctity of closed doors. Wouldn’t, uh. Pull out a razor when his unsuspecting partner was sound asleep after a particularly invigorating round of sex.
“No,” Stiles said, setting the razor down and wiping his fingers - fuzzy from the now admittedly terrible idea - against his pajama bottoms. “You’re still mad. I’m staying in here until you calm down.”
“Stiles. I’m not mad,” Derek lied.
“You’re lisping. That means your fangs are still out.”
Stiles heard a huff and a soft crack as Derek shifted his bones back to their fully human form. “Not mad,” he tried again, this time without the soft slurring that Stiles secretly adored. “Now get out here so we can talk.”
“You’re not going to rip my head off?”
“Not all the way. You’ll probably heal.”
“You still sound like a total creep when you joke like that,” Stiles informed him, opening the door to find his - boyfriend, maybe? assuming Stiles didn’t screw anything else up - sitting against the frame, his feet propped up on one side and his back firmly pressed against the other.
“Good thing you’re into it, then,” Derek said dryly, his eyebrows pulling down in a too-familiar glare that Stiles hadn’t actually seen targeted at him in a couple of years.
Stiles scratched uncomfortably at his chin. “Can I, uh. Can I see it?”
Derek’s eyebrows intensified, but he gracefully stood to his feet and turned around. He cracked his neck, shook out his shoulders, and after a moment, a soft sheen of fur rippled down his back. In, uh. Patches. That spelled out “STILES WUZ ERE” with a clumsily dick-shaped arrow pointing to Derek’s gloriously naked ass.
As usual, Derek had fallen asleep before Stiles and had then woken up at the crack of dawn to start his morning routine. Most mornings, that meant a run through the Preserve, followed by a hot shower and some sort of appealing breakfast plus coffee combo that drew Stiles out of bed. Sometimes, Stiles could be coaxed into the shower with him before the coffee, but only if he didn’t, as Derek termed it, flop around like a dead octopus that’d been glued to their mattress.
This morning, though, Derek had apparently caught a glimpse of himself in the mirror before Stiles had a chance to explain. He hadn’t bothered to pause to pull on sweatpants before pouncing on Stiles - who’d dangerously fallen asleep holding the evidence - and chasing him across the house.
Stiles had to drag his eyes away from Derek’s ass and swallow heavily, reminding himself that they were fighting, and now was not the proper time to press himself against Derek’s back and kiss his beautifully arched throat.
“Stiles!” Derek snapped, smelling the interest on him despite his best attempts.
“I’m sorry! I can’t help that you’re so fucking beautiful.”
“Not right now, I’m not,” Derek muttered darkly, and Stiles could see the embarrassed flush starting in his ears and working its way down his neck.
“Untrue,” he said, because Stiles genuinely couldn’t think of a single scenario in which Derek wouldn’t be the most attractive person he’d ever met. “It’s kinda hot, actually. In a weird way.”
Stiles made an exasperated face at the back of his head. “I could be telling the truth. If you’d just tune down your wolfy ears a bit.”
Derek turned back around, probably so Stiles could witness the sheer amount of effort that went into his epic eyeroll. “I don’t need superhuman hearing to be able to tell that you’re lying. I look ludicrous. You shaved your name into my back. I’m surprised you managed to spell that right, when you got everything else wrong.”
“Hold up a minute,” Stiles said slowly. “That’s the part that annoys you the most? The bad spelling?”
“Yes,” Derek hissed. “No. I’m pissed off about all of it. But how the hell did you forget the ‘h’ in ‘here’? We weren’t even drinking last night.”
“Alcohol occasionally fuels my genius, but is not a requirement,” he stated proudly, but his self-satisfaction ebbed when he got a solid look at Derek’s face for the first time that morning. Derek had been telling the truth, more or less - his eyes weren’t angry. Beyond the surface irritation he was playing up, they were wide and sad, with a guarded edge to them that made Stiles feel infinitely worse. It’d taken years to build up enough trust for Derek to not only fall asleep in his beta-plus shift, but to sleep soundly through the entire process of Stiles finding a razor, nearly slicing his palm open on the blade as he tripped over the trailing edge of a blanket, and snickering to himself as he shaved Derek’s furry back into a pattern.
“To be fair,” he tried again, putting as much apology into his eyes as he could muster, “I’d sorta assumed the rest of your hair would just...sprout right out to fill the gaps when you shifted again.” He made a popping motion with his hands to demonstrate what he’d envisioned.
“That’s not how it works,” Derek said, his eyebrows conveying a more detailed message about exactly how idiotic and ill-informed Stiles was. Stiles paused to be grateful that he hadn’t made the mistake of shaving those off while Derek slept - they would’ve lost about 80% of their ability to communicate - before plunging on.
“I realize that now. And I’m sorry. Really, I am. It seemed funny at the time, I guess.” Still would, actually, if Derek would just stop looking so goddamn heartbroken about the entire thing.
“I’m sorry, too. I thought you were twenty-two, but I must’ve gotten your age wrong by about a decade.” With that parting shot, Derek seemed prepared to leave - the room, definitely, maybe the house as a whole and Stiles’s entire life if he didn’t do something to fix this unexpected mess.
“Hey, hey, no. Come back and be mad at me some more.” He knew his voice had rapidly crossed into pleading, but he couldn’t stop the throb of terror in his throat. He’d been teasing him, that was all. But trust meant so fucking much to Derek. After years of almost being something but never quite managing to get all the way there until Stiles had graduated and returned to Beacon Hills - to stay, he’d insisted, tugging at Derek’s clothes and panting into his mouth - he couldn’t bear to lose it all over something as stupid as a goddamn razor.
“I’m just going to put on some pants,” Derek sighed, returning for long enough to drop a grumpy kiss at the corner of Stiles’s mouth and squeeze his biceps reassuringly. “Then you’re going to shave the rest of this off so I don’t have to wait weeks for your fucking terrible grammar to get covered up.”
“Oh,” Stiles said, and retrieved the razor before following him to their bedroom, where Derek tossed around clothes for an unnecessarily long time before tugging on the first pair of pants he’d touched and discarded. He then huffily flopped chest-first onto the bed and looked expectantly over his shoulder at Stiles. Flopped wasn’t the right term, though, Stiles thought as he crawled onto the bed and settled himself over Derek’s firm thighs. Stiles would’ve flopped on the bed. Derek made even that movement seem majestic, somehow.
He stroked over the hair - fur? - still left on Derek’s back. He wasn’t sure how to label it, but it was soft under his fingers, and he was already mourning its loss. It’d taken him years, too, to discover how many variations Derek could shift into between his fully human and fully wolf forms. The beta shift, as he and Scott had dubbed it during their early experiences with werewolfy powers, was actually the simplest form - a defensive shift born out of a need to rapidly sprout teeth and claws to fight off attackers. When Derek finally relaxed and let down his guard, Stiles was able to see how extraordinary he truly was - although that had never really been a question in Stiles’s mind.
Derek’s human face wasn’t the default one, by any means: it was the one he used most, since the vast majority of society remained sadly ignorant of the supernatural beings in their midst, but the fangs and fur were as much a part of him as his insanely iridescent eyes. And Stiles loved every inch of him. Especially the way his sideburns popped out and his eyebrows disappeared when he sneezed, which was a delightful discovery he’d made while dragging Derek past the perfume counter during Lydia’s birthday shopping spree.
“Do you want me to put a towel down or something?” he asked, leaning down to press a kiss against the heart-shaped dot over the ‘i’ in his name.
“You didn’t bother last night,” Derek said, folding his arms so he could prop his head more comfortably on them. “I don’t understand how you fell asleep in a pile of my hair.”
“It did itch a little,” he admitted. “But I was pretty worn out.”
“Not enough to keep you from being an asshole.” Derek shot a sharp look at him, full of promise. “We’ll see about fixing that tonight. Now get moving, and I hope you know you’re doing the laundry after this, too.”
“That is an unfair punishment,” he groaned, but he grabbed for the glass of water and bottle of shaving cream he’d left on the nightstand. He lathered up Derek’s back more carefully than he had the previous night and held the razor at the ready.
Derek patiently waited for a few beats, then twisted to try to get a better look at his face. “What’s wrong now?
“Nothing’s wrong.” Stiles swallowed past an inrush of sorrow in his throat. “It’s - well, it’s the first time I’ve ever been able to leave a mark on you. Kinda sucks to erase it.”
“Oh for fuck’s sake,” Derek said, impatience thrumming through his muscles. “You realize I can stop my healing for a while if I want, right? If you’ve been wanting to leave hickeys, all you had to do was tell me.”
“Really?” Stiles breathed, picturing the shape of his mouth blooming on Derek’s perfect skin, under the agonizingly beautiful curve of his collarbones, where no one but the two of them would see it. “You’d do that for me?”
“Obviously. Now shave my fucking back; this is awful.”
Later that night, Derek prodded at the oversized, aggressively red bruises stretching across half of his chest and gave Stiles an enormously judgmental look.
“I’m sorry!” Stiles said, doing his best to not give in to the laughter that kept threatening to escape. “I’ve never actually tried to give anyone a hickey before. I just knew you’re supposed to suck. I didn’t know how hard. Or how long it takes for it to work.”
“We’re ridiculously bad at this,” Derek said, falling elegantly back into bed, his arms braced on either side of Stiles’s head. “I think we’re going to have to practice more.”
“I’m a quick learner,” Stiles agreed, pulling Derek down so he could gently scrape his teeth over that spot just behind Derek’s ear that always triggered him to shift to his wolfy face. He shivered in pleasure at the responding pressure of Derek’s fangs - never hard enough to break the skin, but a constant reminder of the immense power coursing through Derek’s body.
“I’ll believe that when I see it,” Derek lisped past his sharp teeth, and Stiles grinned at the challenge.
On their wedding night, Derek fell asleep first, which he did every night, true, but he really should’ve known better, Stiles thought as he uncapped the bottle of shaving cream and wielded the razor. By this point, it was basically tradition.
He woke up to Derek’s horrified shout. “What the fuck, Stiles? Did you seriously shave ‘just married’ into my back?”
“I spelled it right this time,” he pointed out, stretching languidly in bed and reaching for Derek.
“When you fall asleep, I’m shaving your balls,” Derek grumbled, giving in despite the frustrated angle of his eyebrows.
“Promise?” Stiles asked. “I’ve always wondered what that’d feel like.”
“You’re impossible,” Derek sighed, but rested his head on Stiles’s chest so Stiles could scratch his fingers along his scalp in that way that always made him go boneless and cuddly.
“I’m yours, though. Permanently, now.” He smiled at the gold glint of his ring, bright against Derek’s dark hair.