The package is on the porch when he gets home from school.
Stiles draws in a sharp breath, glancing around to make sure none of the neighbors are hanging around, waiting to ask what's in the plain brown box. There's no one there, of course, but he snatches it up and stumbles inside anyway, clutching it to his chest. His heart is pounding and he leans back against the front door for a moment to catch his breath. Dad won't be home until late, which gives him the entire afternoon to himself.
He locks the front door and takes the stairs two at a time, flinging his backpack to the floor as soon as he enters his room.
"Are you okay?"
"Shit, fuck!" Stiles yells, startling so hard he fumbles with the box and loses his grip.
Derek – fucking creeper, hiding in Stiles' room when he isn't even there – catches it, because of course he does. He raises an eyebrow and watches as Stiles tries not to go into cardiac arrest.
"Oh my god, what the hell," Stiles finally says when he can catch his breath. His heart is still pounding, though, because Derek is still here, holding the box with Stiles' brand new dildo in it.
"Your heart's been going crazy since you were downstairs," Derek says, shaking the box a little. "Is it because of this? What is it?"
"It's nothing," Stiles says, probably a little too quickly, trying to reach for the box. "Why are you here?"
Derek narrows his eyes and steps back, moving the box out of reach. "It smells like silicone."
"Oh my god," Stiles says again, and runs one hand down his hot face. "Seriously, why are you here?"
Derek doesn't answer, and when Stiles risks dropping his hand to look at him he can't help but groan. There's an evil, evil smirk spreading its way across Derek's face.
"Yes, really," Stiles says through gritted teeth. "Now, if you could please leave –"
Derek sets the box on Stiles' desk, but instead of moving towards the window he taps his – claws, those are definitely claws – against the top of the box. His expression is considering and, if Stiles had to label it, almost nervous. "Would you show me?"
Stiles blinks. "You want to see my dildo."
"No." Derek's eyes darken. "I want to see you use it."
Stiles makes a strangled noise, wincing as his dick goes rock hard at the visual Derek's words are giving him. He darts his tongue out over his lips, breath catching when Derek's eyes drop to his mouth. His heart hasn't slowed down at all, and he only notices that his hands are trembling when he goes to scratch awkwardly at his elbow.
"Um. Why? I mean, I'm not saying no, I just. Don't understand?"
Derek hesitates, and for the first time since Stiles walked in he looks uncomfortable. He scowls, shrugging slightly. "You're a pain in the ass, but – fuck, you're seventeen. I'm not going to wax philosophic about my extremely inappropriate feelings for you, Stiles."
Stiles gapes, stunned. "You like me. And you want to watch me –"
Derek rolls his eyes, but a flash of something Stiles might call insecurity crosses his face. "Yeah, I do. If that's okay with you."
Stiles stares at him for a moment, trying to process this new information. He thinks that Derek is asking more than to just watch; he's asking if maybe Stiles feels the same way. Glancing between Derek and the box, Stiles swallows hard and reaches for the hem of his t-shirt.
"Open it," he says, voice hoarse, and drags his shirt over his head.
Derek lets out a shuddering breath and immediately slices through the tape on top with one claw. He opens the flaps, reaching in to pull out the bright red cock and the premium bottle of lube Stiles had ordered with it. It looks obscene in his hand, and Stiles is reminded of why he picked that color when Derek's eyes flash red.
When Stiles is naked – holy god, he's naked in front of Derek – he clears his throat and grabs the dildo and lube out of Derek's hands, climbing onto the bed. Derek doesn't take his eyes off of Stiles as he settles in the desk chair, sitting low with his legs splayed out in front of him. It's sexy as fuck, and Stiles groans when he sees the outline of Derek's dick through his jeans, obviously hard.
There's no way he'll be able to keep it together if he can see Derek while he's doing this, so he rolls over onto his stomach. His ass is in Derek's direct line of sight, and he flushes hotly when he hears Derek make a noise that sounds appreciative.
Stiles has been using his fingers while masturbating for ages now, so it's nothing to pour a little lube on them and work them in. He starts with one but it isn't long before he's up to three, breathing harshly through his mouth as he works himself open, his hips rocking against the bed. He's hyper-aware of Derek behind him, watching as Stiles' fingers pump in and out of his hole.
"Come on," Derek says, and it comes out hoarse and almost desperate. "Use the cock, Stiles. I want to see it stretch you open."
"Jesus fuck," Stiles groans, dick giving a hard twitch. He pulls his fingers free and reaches for the dildo he'd set next to him on the bed, slicking it with a generous amount of lube. He presses the tip against his hole, pausing to take a deep breath and say, "I've never done this before, so if I'm not any good at it I'm sorry."
Stiles doesn't wait for Derek's answer, pushing the cock past his rim. It burns and he grunts, but he doesn't stop, working it in slowly with gentle little thrusts.
"Fuck," Derek breathes, and Stiles hears the sound of his zipper. "You've never – in front of someone or at all?"
"At all," Stiles manages, twisting the cock as he pushes it deeper. His fingers suddenly brush against his stretched hole and he groans, realizing he's got the entire thing inside of him. "I heard – are you touching yourself?"
"Yeah," Derek says, sounding strained. "You look so good like that. You've got that entire cock inside of you, and you're taking it so well. I can see you stretched around it. How does it feel?"
"Fucking huge," Stiles says, and chokes out a laugh. "If you keep talking like that I'm going to come before I have a chance to even enjoy it."
He doesn't wait for Derek to say anything else, dragging the cock out slowly and pushing it back in with a bit more force than before. A broken sound tears its way out of his throat, sparks flying up his spine, and he can't stop the full body shudder that goes through him.
"Oh my god, I wish this was you," Stiles says before it even registers that he's going to, eyes fluttering shut. "Is your dick bigger than this one, Derek? I bet it is."
Derek swears again, and Stiles hears the desk chair creak. He thinks Derek is just getting into his own fun, until he feels the bed dip behind him. His eyes fly open but before he can twist to look behind him he feels Derek's hand land flat between his shoulder blades.
"Do you want me to fuck you, Stiles?" Derek says, and his other hand wraps around Stiles' wrist, pulling it off the base of the cock. "Do you want my dick inside of you?"
"Oh fuck," Stiles gasps as Derek grips his hips with both hands and hauls him up onto his knees. "Y-yes, god, so much. Please fuck me."
"Not this time," Derek says, pressing his body against Stiles'. He's still fully dressed except for his dick, which is a hot, hard line against Stiles' thigh.
Stiles doesn't get a chance to ask if there's going to be a next time – all evidence points to yes, anyway – because Derek reaches for Stiles' dick with one hand, wrapping his fingers tightly around the base, and grabs the end of the dildo with the other. That's all the warning there is before he starts fucking Stiles with it, hard and fast.
"Fu – uck," Stiles chokes out, back arching and dick giving a hard twitch. If Derek's grip on it wasn't so iron-tight he would be coming right now.
"Yeah," Derek breathes. "Look at you. First time anything's been in your ass and you fucking love it."
Stiles can't answer, mouth parted on a long, silent gasp, Derek continuously fucking the cock into him without letting up at all. He's shaking, dick painfully hard, and as soon as he's able to catch his breath he starts making embarrassing high-pitched noises, his hands twisting so hard in his sheets he thinks he hears them rip.
Derek groans and the dildo suddenly stops moving at all, shoved deep. Stiles wants to complain but all of his words seem to have disappeared. Derek lets go of his dick, making Stiles whimper, and moves more fully behind him.
"Legs together," Derek says, tapping the outside of Stiles' thighs.
Stiles shuffles awkwardly, trying to obey, the cock inside of him shifting and making him groan. Derek reaches for the discarded bottle of lube and Stiles can hear the slick sound of it as he spreads it over his dick. When Stiles' knees are pressed tightly together, Derek straddles his legs and grips his hips, sliding his dick between Stiles' thighs, nudging against his balls and rubbing along the underside of his cock.
Stiles whines, and Derek presses the fingers of one hand against the base of the dildo, holding it in place. His other hand slides up Stiles' stomach to his chest, and pulls him up so that they're pressed together, Derek's shirt oddly cool against Stile's skin. Stiles groans and drops his head back against Derek's shoulder – and Derek's hand continues sliding up, until it's wrapped lightly around Stiles' throat.
"Is this okay?" Derek asks, and when Stiles nods frantically he tightens his grip until Stiles' breath is coming short and shallow. There are sharp pricks against his skin where Derek's claws are sliding out, and Stiles digs his fingers into the denim of Derek's jeans.
Derek starts snapping his hips, his dick sliding slick between Stiles' thighs, dragging along his balls and the tip hitting the base of Stiles' cock. Derek's fingers are still pressed to the base of the dildo, and he can't fuck Stiles with it like before but the slight movement he does manage is driving Stiles insane. There's a hot buzzing under his skin, his eyes half-closed and lips parted as he drags in sharp, quick breaths against the pressure on his throat.
"So beautiful," Derek murmurs, mouthing over Stiles' shoulder. "I'm going to fuck you properly next time, shove my dick so far in your ass you'll feel it for days afterward. Fill you with my come, maybe one day you'll let me knot you –"
Stiles hadn't realized that was even a possibility, but as soon as his pleasure-hazy mind wraps around the words he's done for, his untouched dick throbbing and pulsing as he comes everywhere. Derek growls, hand disappearing from Stiles' throat as he moves it to the back of his neck and shoves his face down against the bed. He pulls the dildo out of Stiles' ass and then presses the tip of his dick to his open hole, coming against it. Hot liquid splashes into Stiles, some of it sliding down over his balls, and Stiles whimpers as his dick gives a twitch, because fuck that's hot.
Derek groans, rubbing his dick through the mess and dipping two fingers into Stiles' hole, pushing more come inside. Finally he shifts away, collapsing onto the bed beside Stiles and staring at him through heavy-looking eyes. Stiles lets himself tip over, sprawling half on Derek and half on the bed.
"Can you really knot me?" Stiles asks, and fuck, his voice sounds wrecked.
Derek smiles, slow and wicked, and buries one hand in Stiles' hair, gripping tight and pulling him into a hard kiss. Stiles whimpers, opening his mouth for Derek's tongue, and has almost forgotten his question when Derek pulls back and nips at his bottom lip.
"I can, if you want me to."
Stiles shudders. "Fuck yes."
Derek's smile turns soft and happy, and something twists in Stiles' chest. He buries his nose against Derek's neck and breathes him in.
"I hope you realize you're never getting rid of me now."
Derek huffs, and cards his fingers through Stiles' hair. "Idiot," he says, but it sounds fond.
Stiles grins and stretches, rubbing his mostly soft dick against Derek's hip. "So how long until you're ready for round two?"