Stiles is still holding Derek's hand when they walk into the bathroom, his fingers long, pale, and thin around Derek's. His pajama bottoms are still pulled down below his butt, the come that Derek spurted over it earlier drying quickly into Stiles's smooth skin.
Derek watches as Stiles has to stretch to get to the shower head, finally letting go of Derek's hand so he can lift it to accommodate them both. Then he tugs off the pajama top and tosses it on the floor, his bottoms slipping down his skinny legs shortly after. It's when the water starts running and Stiles yelps at the temperature that Derek comes back to his senses a little and pulls himself out of his reverie.
He almost falls right back into a daze when Stiles steps under the spray and rubs his hands down his chest.
"C'mon, you gonna help me or what?" Stiles asks, eyes dancing with amusement.
"I thought you were old enough now," he says, but he's already tugging off his shirt and then sliding his jeans past his hips.
"You're here to take care of me, aren't you?"
"I'm just here to watch," Derek counters, eyebrow raised in challenge.
"'Kay, watch then," Stiles says defiantly.
Derek's just stubborn enough to stay where he is when Stiles squirts some shower gel into his palm and starts rubbing it into his skin. His body looks almost smaller when it's under the spray of water than it should, almost like he's younger than his nine years. Derek shudders but his cock twitches in renewed interest, despite having come only a few minutes earlier. Then again, he is a teenager and a werewolf, his refractory period is not long under normal circumstances. Right now, he feels like he's in one of his dreams, watching as Stiles rubs himself everywhere.
And it is everywhere. Stiles rubs his hands over his arms, down his chest, over his stomach that's almost flat but not muscular, covered with a layer of baby fat that Derek knows won't go away for at least another two years. Then he reaches between his legs and to the tiniest patch of emerging hair there, over his small cock and to the balls hanging behind it. He spreads his legs like he's trying to find a way to make himself more steady, then his fingers tug on his length, most of it fitting into his palm. Derek thinks his own hand would maybe cover both the cock and Stiles's balls.
Then Stiles turns around, bends forward a little, and lets the spray of the shower run down his back, his hands bracing on the wall in front of him. Then he glances over his shoulder at Derek and has the audacity to stick his tongue out as he sticks his butt out in Derek's direction.
That breaks Derek's resolve, whatever was left of it. He steps forward and he's reaching out to put his hands on Stiles's hips before he can think about it.
"I think you might need a little help washing," he says. "There seem to be some places you can't reach."
Stiles nods and faces forward again, his feet inching further apart. Derek swallows when he sees the way that exposes Stiles's pucker, dusky red and twitching like it's trying to summon Derek's finger back inside. He rubs his thumbs down the length of the cleft, marvels at the way his palms cover Stiles's buttcheeks almost completely. He doesn't have big hands, but Stiles is so small that it's enough, he's so skinny that Derek's spread out hands cover everything from the cleft all the way to the front, his fingers resting right on top of the dip of Stiles's hipbones. He spreads Stiles's cheeks a little more and watches as Stiles clenches his hole then relaxes it.
Then he has an idea. He lets go and climbs into the bathtub next to Stiles, puts his hands back on Stiles's sides and turns him -- Stiles doesn't protest, doesn't offer any resistance at all -- until he's facing the wall on the shorter edge of the tub and Derek's behind him. He's bent forward before Derek crouches down in the tub, drops from the shower bouncing off Stiles's smooth back and onto Derek's face. Stiles glances over his shoulder and frowns in confusion.
"What are you...?"
Derek doesn't answer in words. Instead, he leans forward, puts his hands on Stiles's butt again and spreads the cheeks open, then he presses his lips against the top of the cleft. Stiles yelps in response and Derek pauses, ready to catch him in case he slips.
"Oh man," Stiles says as his head falls forward again.
He clenches his butt, tenses up but doesn't move as Derek watches.
Then Derek kisses his skin again, from the top of the cleft along one side and around his fingers, until he reaches the spot between his hole and his balls. Stiles lets out another yelp when Derek sticks his tongue out and runs it over the sac and then upwards. The scent is strong here, even when it's mixed with the water that's running down Stiles's back and between his cheeks.
"Der..." Stiles starts, the word cut off as Derek moves his head upwards, lining kisses along the other butt cheek.
Then, content that Stiles is still steady on his feet and that he's prepared to catch him, Derek spreads his butt open again, thumbs next to his pucker, and watches as the water runs over it. Stiles seems to be feeling it if the way he's already trembling is anything to go by. The way he's so sensitive to everything, the way he reacts like -- because, Derek reminds himself -- it's all a first is mesmerizing and it makes Derek's cock throb. He's already hard again, the sight of Stiles's pucker twitching adding to his own arousal. He moves his thumbs closer, rubs them over the rim and listens as Stiles's heartbeat quickens yet again.
It's when he leans in and runs his tongue over the hole that Stiles's knees seem to give in. Derek pulls away and steadies him, then he gets up and tugs Stiles to his chest. He's reminded of their size when his chin rests on top of Stiles's head.
"Too much?" Derek asks, arms wrapped around Stiles's shoulders, cock hard against the small of his back.
"Nuh-huh," Stiles replies, but it's hesitant.
"Hey, it's okay," Derek tells him, rubbing his palms over Stiles's stomach. "Let's get you clean.”
Stiles nods but doesn't move, his arms limp by his sides, back leaning against Derek's chest. Derek trails his hands over him like this, then reaches for the shower gel and starts rubbing it into Stiles's skin. When he gets to the small nipples he gives them a gentle tug, earning himself another yelp and a gasp. Stiles stands still -- maybe for the first time since Derek's known him -- and lets himself be washed thoroughly. Derek's hands cover his arms, wrap around his biceps, then he chuckles when Stiles squeaks as Derek lifts one arm at a time and washes his armpits.
"Gotta do all the places," Derek whispers, then he runs his hands down Stiles's sides and rests them on his hips.
He doesn't turn Stiles around. Instead, he leans forward and looks over Stiles's shoulder, then watches his own hands spread over Stiles's crotch, fingertips at the base of his small cock. It's not quite hard, not the way Derek's gets, it won't be for another little bit. But it's chubbing up just enough. Derek gives in and takes it into his hand, hearing Stiles's shaky breathing and rabbit-like heartbeat. Stiles's head falls back against Derek's shoulder as Derek fondles the cocklet. Derek reaches his free hand up quickly to move the shower so it's not right in Stiles's face, then he returns his hand down and onto Stiles's ballsac. He's rewarded with another gasp and a grunt, then a tremble that runs through Stiles's body as he seems to come. There's too much water to tell if there's anything else dripping from his cocklet, but Derek doesn't care.
His own hips stutter against Stiles's back, the tip of his cock pressing into it.
"Can I try something?" Derek asks then.
Stiles nods and seems to get control over his limbs again, though he lets Derek move him again, back to how he was earlier. He's bent forwards, but Derek moves his legs so they're together. Then he bends his own knees as he moves forward, humming with content when his hips line up with Stiles's ass. His cock is right against the crack and Derek holds back a moan as his hips jerk forward instinctively. He can just imagine doing this, continuing, rubbing his cock against Stiles's soft skin and then coming all over his back.
He shakes his head and stops though, then reaches to his cock and angles it down, bending his knees a little more. The water is splashing down between them and Stiles tenses when Derek's cock comes to rest under his balls.
"Put your legs together, baby," Derek says quietly.
There's enough moisture and glide from the water that when he pulls his hips back, the movement is smooth, his cock in the tight crevice between Stiles's thighs. When Derek thrusts forward, the tip of his cock peeks out at the front of Stiles's legs, bumps into Stiles's cocklet. The contact sends sparks through Derek and his cock throbs.
"Now, hold still, okay?"
Stiles nods, head down between his arms that are braced against the wall, then he arches his back as he lifts his head up and looks at Derek over his shoulder. Derek holds his hips gently and starts sliding his cock between his thighs, slow at first, watching for changes in Stiles's face. Then, as his cock starts throbbing again and his balls start drawing up, he speeds up and his hips bump against Stiles in a steadier, faster rhythm. He can just imagine doing more, driving right into Stiles's tight asshole, filling him up to the hilt. He can feel the base of his cock reacting to that thought, can feel it thickening as his balls tighten Then Stiles drops his head between his arms again and Derek's eyes fall on his exposed neck. He feels his gums tingling, the fangs so close to dropping, his fingers buzzing with the need to sprout claws, and he knows that his eyes are glowing blue.
A quiet whimper from Stiles's lips reminds him that he can't, that Stiles doesn't know about werewolves. The shudder that runs through Stiles's body right after, another tiny orgasm, trips Derek over the edge. He thrusts between Stiles's hips one more time, holds them in place as his cock spurts come onto Stiles's small cock and down onto the bathtub. His own body shakes with the strength of the orgasm and he barely manages to keep his balance.
It's better when he pulls away a moment later and straightens his knees, bringing Stiles's lithe body against him again. He leans down, raises a hand to Stiles's face to turn it back to him, then kisses him gently.
"Such a good boy," he whispers. "So good."
He's not sure if Stiles can hear him. The boy's face looks dazed and like he's dreaming. Derek kisses him again and then goes back to washing him up, gently rubbing his hands all over Stiles's body, peppering kisses in places. He grins when Stiles whimpers after a tender kiss to his bellybutton.
"No more tonight," Derek mutters in his ear a moment later. "Let's get you to bed."
Stiles nods, looking a little sleepy again, like whatever boost of energy that he had has seeped down the drain. Derek can't help but smile all while he's rubbing Stiles's skin dry and then as he rummages for clean pajamas. Ultimately he just grabs a pair of tiny briefs and an oversized tee from Stiles's wardrobe. When Stiles is in bed and looking up at Derek, still with the same dazed expression, Derek glances down at the towel around his waist.
"Well, this is gonna be a problem," he says.
"I can't stay naked, Stiles," Derek tells him with a frown. "What if your Dad comes home?"
"Got food on your clothes," Stiles offers. "Works for me every time."
"Even if I wash my clothes now, how am I gonna get home?" Derek asks -- more musing to himself than actually asking Stiles.
But in response, Stiles scrambles out of the bed, all arms and skinny legs and pale skin, and leaves the room. He's back moments later with a pair of sweatpants and a tee, obviously his father's.
"Dad won't mind. Was in the spares cupboard," Stiles says and punctuates his words with a yarn. "Come sleep."
"I'll--" Derek starts, looking at the clothes in his hands and then at Stiles. "I need to go wash mine."
Stiles looks at him, his lips in a pout. Derek sighs and watches him as he puts the sweats and tee on, then nudges Stiles to the side. The bed is only just big enough to hold them both, at least until Stiles decides to roll on top of Derek, resting his head on his chest.
Derek doesn't sleep for some time. Even after Stiles's breathing evens out as he falls asleep, he watches his own chest rising with the boy on top of it. He wonders if he could forget about what happened tonight. If he could make himself forget. But then Stiles wiggles in his sleep, a quiet "Derek" spilling from his lips. And Derek knows that he won't. That he can't. That there's no going back.