(Not) Limited by Blood

This is the story otherwise known as "The Role of the Sharingan in Sex and Endogamous Bonding and Incidentally Kakashi’s Massive Control Issues". I’m really not sure I can summarize it better than that. Written for the Porn Battle prompt: Kakashi/Sasuke, teacher. Porn with Characterization and Worldbuilding, I-4

Warning: clan endogamy may result in incest-y vibes for some.

Pairing(s): Kakashi/Sasuke

Look, I never claimed to be in control of the bunnies I get from this fandom.

This takes place when Sasuke et. al. are about 19.

Sasuke stood out on one of the curving verandas that every building in Tanigakure seemed to have and wondered distantly how soon he could get out of here. He pressed his forehead against one of the veranda’s smooth wooden posts and closed his eyes, breathing in the faint, rising cool of the river flowing through the bottom of the valley. He wanted to be gone from this place.

Not because Hidden Valley was a trial to stay in or anything. It was a pleasant village, and if the sloping sides of a deep gorge seemed like a precarious place to build a village, at least the floor and lip of the valley were thick enough with trees to make him feel at home.

Not because the mission was going badly. It was going fine from what he could see. Valley’s council had agreed to relax the border controls between River and Fire countries, to allow larger groups of Leaf shinobi across as long as they presented proper notice of their mission at the border, instead of having to wait for approval from the village. The Master of Valley even seemed a bit charmed by Kakashi, and even her most uptight councilors seemed to approve of Sasuke.

Oh yes. Sasuke knew why the Fifth had sent him along. Over half the council were members of the Yasumori clan, and Yasumori was a clan like Hyuuga, like Uchiha had been—old and dignified. The longer he was here, the more Sasuke found himself falling back into old habits, found formalities coming easily to his lips, found himself reading at a glance the little indications of clan politics, of who was supporting or feuding with whom. It was exactly what Kakashi needed as he dealt with the Yasumori, so here Sasuke was.

And it hurt.

Every time he bowed at just that angle that said he was a son of the senior branch; every time one of the Yasumori unthinkingly cleared the way for him in response; every time he recognized the tiny grimace that said Yasumori Koujirou really wanted to disagree with Yasumori Michiru no matter what their clan head had told them about solidarity in front of outsiders; every time he saw those things and looked by reflex for familiar eyes, eyes like his, and found only the green and hazel of Yasumori, it hurt.

Maybe it would have been better if Naruto or Sakura had been along on this mission. Maybe they would have been able to remind him that he was someone else, now, building a new clan and not the son of an old one. Maybe that would only have made it worse; he didn’t know. All he knew was that he thought he might give his soul to look into eyes like his own tonight, and the last of those in the world were both traitor and dead.

“Sasuke?”

Kakashi’s voice startled him, but he stifled a flinch (because a noble didn’t show his reactions like that) and raised his head. It was starting to get dark and his teacher was a shadow in the cool dimness under the veranda roof. “Is there a meeting?” he asked steadily.

Kakashi’s visible brow quirked just a bit. “No meeting. And it looks like that’s just as well.”

Sasuke flushed. He should be concealing his hurt better than that. “I’ll be fine,” he insisted. “It’s just…” He bit off the explanation.

“Hm.” Kakashi came to lean silently on the veranda rail beside him, looking down over the curved roofs below them, fading away into the gorge as dusk fell. Only a few lamps had come on, yet, to re-trace the outlines of the village. It was quiet here where the guest houses stood, and the soft rush of the river below blended with the murmur of people a handful of steep, wooden streets away. “It’s just what?” Kakashi asked, just as Sasuke was relaxing again.

“Familiar.” It slipped out without thought, and Sasuke gave his teacher a quick glower for getting that out of him.

“I did wonder about that,” Kakashi murmured, not minding the glare at all which was just typical. “Unfortunately, I was the only jounin free to send on this one and you were the only noble of a senior branch free to come. At least the only one I could trust to tell me all I need to know.”

That confidence in him warmed and hurt, both. “I’ll be fine,” Sasuke repeated, with determination if not quite as much surety as he’d have liked.

“Hmmm.”

Sasuke stiffened at first, but the sound wasn’t doubtful; just thoughtful. Of course, that wasn’t any less alarming for anyone who knew Hatake Kakashi.

Even knowing that, though, he wasn’t prepared for Kakashi to straighten and casually push up his forehead protector, looking down at Sasuke with his Sharingan uncovered. After days on end of furiously suppressing his desire for his own clan, the reminder that there was another Leaf shinobi with Uchiha eyes hit Sasuke like a fist in the gut and stopped his breath just as surely.

“I wondered,” Kakashi repeated quietly, and lifted a hand to rest on Sasuke’s shoulder, warm and sure, just holding him.

Sasuke caught his breath again in a deep gasp, and a confusion of words and thoughts tumbled up to his lips. “Sensei… I mean, senpai… I… Kakashi-san…” In his heart it was none of those, but he didn’t dare say it. It would be too much.

Kakashi’s hand tightened, strong and reassuring, and the tangle of want in Sasuke was joined by a simpler, more familiar heat that made his breath hitch a little. He swayed forward before he caught himself, uncertain. He thought Kakashi smiled just a little behind his mask, and a thumb stroked up and down his neck gently.

“It’s all right,” Kakashi told him, soft as the deepening dusk. “You’re my team here, Sasuke; you know I’ll take care of you.” And then Sasuke just had to stand and stare, because he hooked a finger over the edge of his mask and slid it down.

When they’d all been younger, his team had schemed wildly to get a glimpse of their teacher’s face. As they’d gotten older, Sasuke had come to understand there was no great mystery, only an entrenched habit of concealment; and he could understand that perfectly well, and had stopped trying to get past it. And now here it was, set aside for him just as easily as this. It was the simplicity of it that let the heart-deep words slip out as Sasuke leaned closer, hands coming up to Kakashi’s chest, the way he would have called any of the older cousins.

“Kakashi-niisan.”

His teacher smiled, a startlingly clear curve of firm lips. “Yes.” He tipped Sasuke’s chin up and kissed him, slow and easy, watching him with that half-lidded red eye, and Sasuke’s heart turned over and sped up. There were things he’d never had the chance to learn but had still heard about; things about how the sight of the Sharingan could be used in bed. The way Kakashi’s tongue stroked over his and swept through his mouth made him wonder if it had all been true, because before long he was clinging to his teacher’s shoulders and panting for breath thanks to that slow, wet slide.

The street lamp outside their guest house came on, casting the fineness of Kakashi’s profile into relief as he finally drew back, making the silver of his hair shine as he tilted his head toward the door. “I think this is better carried on inside, hm?”

Sasuke swallowed and murmured, husky, “Yes, Kakashi-niisan.” He expected Kakashi to turn the lights on when the door closed behind him, but the room stayed fully dark, and Sasuke’s eyes widened as he understood. He took a breath and activated his own Sharingan, and a flash of hope and excitement ran through him as the shapes of the room faded into his sight, dim against the shifting brightness of Kakashi. The thought of having an older clanmate again (kind of; close enough!) to guide and teach him made him shiver—hard enough that, when Kakashi held out his hands, Sasuke stumbled going to meet him. It had been so long.

He was caught and pulled close against the heat of Kakashi’s body, feeling it and seeing it, and when Kakashi’s hand slid down his back to just the right place to support him he knew he was being seen the same way. “Please,” he whispered, and lifted his face to meet Kakashi’s mouth on his.

Their clothes ended up scattered across the room, a vest flung over one chair, Sasuke’s shirt dropped onto the low table, Kakashi’s pants kicked into the corner, and when Sasuke finally got to feel the the sleek heat of Kakashi’s skin against his own he moaned. He could see every shift of response in Kakashi’s chakra as his hands traced over the solid muscle of his teacher’s back and shoulders, and knowing he was just as bare to Kakashi’s eyes, to his Sharingan, was enough all by itself to make him hard.

And it wasn’t all by itself.

Sasuke came up onto his toes, body arching helplessly taut as one strong hand closed between his legs and calloused fingers stroked his cock knowingly. “Kakashi-niisan,” he gasped, wanting, almost pleading, and Kakashi’s fingers tightened as he caught Sasuke’s mouth in another kiss, deep and hard. Sasuke lost it all in a second, coming with a strangled groan as heat wrung him out fiercely, over and over, until he was leaning against Kakashi and gasping for breath. “Wha…”

“Mm. Now maybe we can take it a little slower,” Kakashi-san murmured against his ear, and Sasuke could hear the smile in his voice, see it in the shift of his chakra. He was sure his hot blush was just as visible, and felt the vibration of his teacher’s chuckle through the broad chest he rested against.

“Yes, Kakashi-niisan,” Sasuke managed, a little embarrassed and a little delighted with the teasing. It felt good, intimate and casual and like clan.

He let Kakashi guide him down to the bed, watching the tight, patient coil of his teacher’s chakra, the focus of it. That focus was in the hands that slid down his body, slow and sure, spreading his thighs until he gasped, kneading the drawn muscles of his stomach until they relaxed into heat, cupping his ass and squeezing just once, hard enough to make him moan. He reached back, for once a little shy next to his teacher’s experience, watching with the clarity of the Sharingan and the dizziness of the heat in him to see what Kakashi liked, what his chakra brightened for. He trailed his hands down Kakashi’s chest to stroke lightly over his cock and was answered by a low sound and swift downward shift of chakra. That gave him an idea, and he licked his lips.

“Kakashi-niisan? Can I…?” He slid his fingers down the length of Kakashi’s cock.

After one still moment, Kakashi’s fingers slid through his hair and tipped his head back for a slow kiss. “Yes,” Kakashi murmured into his mouth.

Kakashi’s hand slid through his hair as he settled between Kakashi’s legs, and Sasuke leaned into his fingers. That made the coiled lines of Kakashi’s chakra ease before Sasuke even touched him, and fresh heat curled through Sasuke. If his teacher wanted to guide him in this, too…

“Kakashi-niisan.” He rested his cheek against Kakashi’s thigh, looking up at him. “Will you show me?”

“Show you?” Long fingers stroked lightly through his hair again, and Kakashi’s voice sounded perfectly casual, but his chakra was still flowing in tight, poised lines.

“How to do this for you.”

For one instant, Kakashi’s chakra coiled even tighter, as if he hadn’t expected Sasuke to see what he wanted. But then it relaxed all at once, spread out into the soft edges of acceptance. The flicker in it matched the flash of wry amusement in Kakashi’s voice. “Yes. I think that will do. For both of us.”

Kakashi’s hand slid down to cup Sasuke’s cheek and guide him down, and the heat in Sasuke’s stomach turned heavier. He opened his mouth and slid his lips down Kakashi’s cock, and moaned as Kakashi’s other hand wove into his hair. This was good. He gave himself up to the signs of Kakashi’s hand against his head, of the long fingers wrapped around his jaw, of the flow and flare of Kakashi’s chakra, moving as he was shown until the thickness of Kakashi’s cock was sliding in and out of his mouth, over his tongue, slow and steady.

And Kakashi was careful with him. Didn’t press him down too far. Kept his hands gentle, even as his breath was coming faster and deeper and his chakra was falling and brightening. It was good, good to feel that, good to trust it, good to watch that sharp, red eye on him in the darkness and know he was being seen by kin, by clan.

(Close enough!)

And then Kakashi’s hand was sliding under his chin, lifting his head. “Enough,” his teacher said, husky. “Come here.”

Sasuke slid back up Kakashi’s body and was caught tight against him, kissed hard as he wrapped his arms around Kakashi’s solid shoulders. The room spun as Kakashi turned them, laid him down, but that was all right because Kakashi’s chakra was steady, a stable anchor like Kakashi’s weight over him. The rush of heat as strong hands slid down his thighs and caught his knees to spread him wide open, so wide, drowned his thoughts and he moaned openly, pinned down under Kakashi’s gaze.

“Mmm.” It was a satisfied sound. “I thought this might do for both of us, yes.” Kakashi’s smile was clear. “Well, since my hands are busy, why don’t you get me ready, Sasuke?” he teased. “I think your vest is by the bed.”

Sasuke flailed wordlessly for his vest and fished in the inner pockets. Knife oil, muscle salve, no, ah there it was. He slicked his fingers with gel and reached down to slide them over Kakashi, completely unable to help the soft moan when he thought about the cock in his hands sliding inside him.

Knowing Kakashi, that was probably the idea.

And his breath cut short again as Kakashi’s eye on him sharpened. “Now,” Kakashi told him softly, and Sasuke grabbed for his arms, fingers closing tight as Kakashi’s cock pressed against him, into him. Slowly. Very slowly.

“It’s all right, Sasuke,” Kakashi murmured to him as he gasped. “I see you. I’ve got you.”

Shudders were running through him under Kakashi’s hands. The stretch of it was hard, just on the edge of too hard but never past it, because Kakashi was seeing him, every flicker of response in his body and chakra, and that had Sasuke making little moans of want, low in his throat. The thick slide opening him just kept going; as soon as Kakashi was all the way in he was drawing back again, smooth and slow, never pausing, fucking Sasuke so steadily that he was half out of his mind with the rush of sensation.

And it just kept going.

His throat was dry with panting for breath he never caught, and his legs were trembling in Kakashi’s hold, and it took him forever to even think to free one hand from their frantic grip on Kakashi’s shoulders and reach down to fist around his own cock. Kakashi made a husky sound at that, and thrust into him harder, and Sasuke’s stroke tightened at the rush of heat. “Kakashi-niisan,” he whispered, pleading.

“Look at me, Sasuke,” Kakashi ordered, velvety in the darkness, and Sasuke looked up to meet the intent eyes above him, caught by that familiar red, focusing his own gaze on it.

And it changed, spinning into the scythe wheel of Kakashi’s Mangekyou Sharingan, the deepest power of their clan.

Response slammed through Sasuke like a wave crashing up the shore and he groaned as fire flashed down every nerve and wrung him fiercely until he was breathless, senseless, aware of nothing but heat and the eye that locked his gaze. His body was wringing down so hard he was barely aware of Kakashi driving into him deep and fast, but he saw the answering brightness flash through Kakashi’s chakra, spilling through like a waterfall. Pleasure sang through him until he thought he might break before it peaked and dimmed slowly with the ebb of their chakra.

They were both still for a long moment before Kakashi gently eased Sasuke’s legs down to the bed again and stretched out, drawing him close. Sasuke lay quietly against him, feeling completely limp and more at peace than he’d been since they took this mission.

“It’s true, you know.”

Sasuke made an inquiring sound, and Kakashi’s hand came up to cradle his head against Kakashi’s shoulder, careful and tender.

“For the sake of Obito’s gift to me, I was affiliated with the Uchiha. There was no other lawful way to respect his wishes. I never claimed anything of the clan, but the fact remains.” His thumb rubbed slowly up and down the tendons of Sasuke’s neck as Sasuke stiffened, mind blank. “You know who your family is now, Sasuke. But if you need clan, too… remember it’s here.”

Sasuke wrapped his arms tight around Kakashi’s chest and whispered against his shoulder, “All right.”

It was a shock. And yet it wasn’t. He’d never suspected it was official, but Kakashi was his teacher, the one he went to when he’d found something new in the clan records, the one who understood what the Sharingan saw and did. The one who had held him and seen him tonight, the way one of his clan would have if there had been time. Sasuke let his breath out and edged closer on the bed.

Kakashi relaxed too, and his lips brushed over Sasuke’s forehead, and Sasuke settled into his teacher’s arms as easily as he would into any of his kin’s.

End