Derek doesn't know who the kid is. He'd say he didn't care, but that isn't true in the least. He does care. He'll care even more when he's finished fucking him. As it is, it took all his willpower to shove the kid into the janitor's closet so they wouldn't be doing it in the middle of the school hallway. The kid doesn't mind. He tripped a little, but Derek thinks that has more to do with his nature than any actual resistance. He lifts his arms willingly when Derek makes for the bottom of his shirt and has no protest on his lips when Derek kisses him.
He tastes like Honey Nut Cheerios, and Derek has a brief thought of being conditioned to get hard whenever he tastes them, but then the kid bites his lip and opens his jeans in the same moment and Derek forgets. He hauls him—his soulmate—into the air and steps to push him into the wall. Only there's a cabinet there and the kid yelps when Derek slams him into it. Derek himself jumps because things start tumbling off the top shelf onto them.
"Floor," the kid gasps. "Come on, go!"
Derek drops obediently, the kid settling onto his hips from above. He doesn't know how he'd managed to find him, but god, Derek loves him. He loves him already, so much. He grabs for his shadowed face and kisses him while those long, busy fingers start moving the fabric between them. Derek turns his mouth to his neck, biting and sucking tiny bruises.
"Name," the kid gasps suddenly, hands braced on Derek's chest. "N-need your name. Tell me, please."
"Derek." he mutters, turning to kiss him again. He can't stop kissing him. It's like their magnetized to each other and each other alone. A fluttering thought of Paige passes, how he'd thought she'd been the one but no, no there was no way because he was. "Yours?"
"Stiles." he presses into his mouth. The name causes Derek to pause.
"Stiles?" he repeats, incredulous. But the name slides off his tongue perfectly, fills the slot inside him he hadn't known existed. It's the perfect name. It's his soulmate's name. "Stiles."
"Okay, now you have to fuck me." Stiles says, nodding eagerly.
Derek nods in agreement, pulling off his shirt while Stiles shimmies out of his own pants. Derek sits up to shimmy out of his, too, but Stiles beats him to it. He tugs the denim down around his thighs and then stops, eyes wide and glinting off the faint light sneaking under the door. Derek hears him breathe something like oh, god but he can't tell and before he can ask Stiles has his mouth around him.
Derek's entire body convulses, a hand flying into Stiles' hair and his heel catching on the ground with a loud squeak. Stiles hums, head bobbing contently, slowly. Derek curls around him, unsure what else to do. "Stiles," he hisses. "Fuck, fuck, Stiles, Stiles, Stiles..."
Stiles lifts his head slowly, tongue dragging and catching on the tip of Derek's cock. "I like the way you say my name." Stiles purrs as he slides up to hover close to Derek's mouth.
"I'll never get tired of saying it." Derek promises.
"Can I kiss you?"
"I'd be really pissed off if you didn't." Derek huffs, dragging him in himself. He tastes like skin and salt and Derek's precome. He tastes perfect.
"Pants." Stiles mutters into his mouth. "Off, please."
Derek strips his jeans, shoes and socks going with it. He'll feel ashamed later about laying butt-ass-naked on the floor of the janitor's closet, but Stiles' fingers are working Derek's dick and he can't not return the favor.
He curls an arm around Stiles' waist, using it to haul him forward. Stiles moans his appreciation for the show of force. Derek takes that as his go ahead to slip his fingers between Stiles' ass and probe at the slick, puffy pucker of his hole.
"Oh, fuck." Stiles gasps, rocking back into it. Derek just barely misses slipping inside him. "Yes, do it. Finger me open, Alpha, please. Want you inside me. Fingers, tongue, cock, all of it. Please, please."
"You're so fucking slick, Stiles." Derek pants. Stiles' hand is still pushing him closer to orgasm. "So ready for me to take you." Derek spears a finger forward a little harshly. Stiles eyes roll back and his fingers tighten. "Take what's mine. You're mine, aren't you? Made for me, only me. I don't care who's touched you before, no one else will ever touch you again."
Stiles grinds back into his hand, nodding frantically. "Yours, all yours, no one else, just you. Only you, always. More."
Derek adds a second finger, moaning when Stiles does. "When I get you home I'm going to lay you down and eat you out so well. Gonna taste my pretty boy, make sure you know that you're mine all over."
"Yeah, yes," Stiles whines. His hand movements are getting sloppy, but it's okay because Derek doesn't need finesse, just friction. He's close enough.
"I'm going to get my hands all over you." Derek promises, but it sounds more like a plea. "Touch you everywhere, smear my come up and down your skin and inside your slick little hole so you can never get the smell of me off you. Plug you up with my knot and pump you full of—fuck, fuck!"
Stiles bites into his shoulder at the same moment Derek comes. There's a sobbing sound coming from one of them, but he can't quite tell who through the haze of orgasm. He twists his fingers a little inside Stiles, which is rewarded with a splatter of come onto his stomach.
It's a few tense moments before Derek realizes he's exhausted and has absolutely knotted in Stiles' hands. He carefully slides his fingers free and turns them on their sides. Stiles snuffles, already dozing, and Derek closes his eyes to do the same.
There's two detention slips waiting for them once they exit the closet, both filled out for the next month. Stiles frames them.