At least four times a week Tsukishima's life was made intensely difficult by dating the captain of the Slytherin Quidditch team, but on this particular Saturday morning, he had to admit it had its perks as well. Not everybody had a boyfriend who could brew a textbook-perfect Polyjuice Potion and then would turn around and use it solely in the name of sexual experimentation.
"Are you sure this is safe?" Tsukishima asked, just to nettle. Kuroo's potions were always fine, even when he made weird ingredient substations, infuriatingly. Tsukishima's potions blew up if he so much as sneezed over them.
"I put in the O in OWLS, Tsukki!" Kuroo said cheerfully. "Also I made Bo test it last night. We turned him into another Lev and I thought Yaku was going to—"
"Do NOT make another Wingardium Leviosa joke," Tsukishima interrupted. Kuroo chuckled, carefully ladling Polyjuice into jars and trying not to drip on the rug. "How long did it last?"
"About three hours," Kuroo said proudly. He had a right to be proud, since the length of the effect was determined almost solely by how skillfully it was brewed. An hour, two tops, would have been average for a NEWT-level seventh year. Not that Tsukishima was dumb enough to praise him to his face, but it was impressive, just a little. "Plenty of time, right? Oh man, Tsukki, we can try everything."
Blushing in spite of himself, Tsukishima wondered if four hours of uninterrupted sex with Kuroo might actually kill him, Polyjuice or no Polyjuice. And that was just how long the potion would last; it would probably still be hours after that by the time Kuroo's roommates returned from their Hogsmeade weekend. Tsukishima somehow doubted Kuroo would suggest a trip to the library right after they changed back.
"Hey," Kuroo nudged Tsukishima's shoulder with his own, "you still in? It's okay if you changed your mind. I will absolutely have a normal dude-on-dude sex marathon with you instead."
Tsukishima waited thirty seconds or so to make it seem like he was actually thinking about it, but really he'd already been thinking about it for the month it had taken Kuroo to brew the stuff, and he'd already decided. It was true that Kuroo definitely had more interest in girls than Tsukishima ever had, but he seemed almost more interested in sex as a girl than he was in sex with a girl. Tsukishima would have felt weirder about it if Kuroo had suggested only Tsukishima try swapping genders, but his pitch hadn't been like that at all. Besides, if Kuroo was having second thoughts about his choice of "dude-on-dude," there were always plenty of Quidditch groupies hanging around with their skirts rolled up, and sneaking off with one of them would definitely be easier than brewing Polyjuice.
The weirdest part for Tsukishima was having to pick the girls they were going to turn into, since they couldn't exactly turn into girl versions of themselves. They'd spent more than one breakfast eyeing and dismissing options while trying to look casual, only to have Bokuto holler, "WHAT ABOUT HER?" loud enough for McGonagall to give them a beady eye from the teacher's table. Fortunately everyone assumed they were helping Bokuto troll for his next infamously short-lived Hogsmeade date. Kuroo had picked Taniyama Hanako, a slight blonde from his house who was attractive, if slightly bookish for a Slytherin. Tsukishima took longer to decide but in the end had picked Fujiwara Reina, a Slytherin Beater who looked like she could put a hippogriff in a headlock and had dark hair only slightly less ridiculous than Kuroo's. Kuroo had approved, teasing Tsukishima about being a Quidditch groupie himself.
"It's fine," Tsukishima finally said. "You already brewed it. You got the hairs, right?" It had been Kuroo's job to work that part out, since both girls were in his house.
"Uh-huh." Kuroo screwed the lid of the last jar down tight. He'd had enough for four or five more doses even after Bokuto's test. "All set! Let's go."
Jars safely tucked in his school bag, Tsukishima's hand firmly held in his, Kuroo led the way back to the Slytherin dungeon. Tsukishima always felt uncomfortable coming into the Slytherin dormitory with Kuroo, but if anybody had something to say about their captain bringing in his boyfriend, they never said it to Kuroo's face in Tsukishima's experience. Still, he was glad that the room was nearly deserted, most of the students already on the way down to Hogsmeade, and even gladder when they were safely in Kuroo's room with the door shut behind them. He also appreciated that Kuroo and his yearmates preferred normal lamp colors as opposed to the eerie green lighting of the common room.
"We don't even have to pull the curtains!" Kuroo said gleefully, flopping down on his bed.
"What if they come back early?" Tsukishima asked, frowning as he picked up Kuroo's bag and set it down on the floor, before Kuroo shattered a jar and ended up drinking Polyjuice out of it with a straw.
"Pfft, don't worry. I told those guys they better not or they're gonna see some stuff they never expected." Kuroo grinned up at Tsukishima unashamedly. "I meant me with tits, but i'm pretty sure they thought I meant you doing something naughty."
"Seriously, Kuroo-san," Tsukishima grumbled. Kuroo grabbed him by the wrist and yanked him down onto the bed, hands already going for Tsukishima's robe fastenings. Tsukishima let Kuroo push him down and kiss him, the familiarity of making out with Kuroo easing some of Tsukishima's nervousness for what they were going to try. Ever a multi-tasker, Kuroo managed to toss aside most of their clothing without interfering with the kissing, although he conspicuously left Tsukishima's tie dangling loosely around his neck. "Seriously, Kuroo-san."
"What?" Kuroo blinked innocently. He laughed it off as Tsukishima pulled the tie loose and tossed it aside. Kuroo sat up. "I guess we better get this show on the road before we get too carried away."
"We?" Tsukishima rolled his eyes, but didn't exactly take them off Kuroo's bare ass as he leaned over the edge of his bed to grab for his bag.
"I'm still going first, right?" Kuroo asked, fishing out one of the jars and handing it to Tsukishima to hold. Tsukishima took it, nodding. "So we'll give it an hour, just to be safe, and then you take yours. Last chance to back out."
"I'm good," Tsukishima said. He was bluffing a little, but he was pretty sure Kuroo knew that.
Kuroo sat the second jar on his bedside table, close at hand but not especially easy to knock over, then cast a murmured tintinabulus on his hourglass. An hour's worth of sand swirled up into the top half of the glass, and then started whispering down. Satisfied, Kuroo set his wand on the table next to the jar, and Tsukishima handed over his as well. Better safe than sorry, and after what happened to Tanaka in fourth year, Tsukishima knew better than to roll over naked onto a wand in bed.
"All right," Kuroo said, holding up the small envelope labeled Fujiwara in his scrawled handwriting. Tsukishima unscrewed the jaw and held it out; Kuroo pulled out a couple hairs from the envelope and dropped it into the Polyjuice. The potion turned dull, leathery red. "Ugh, that's appealing. Bottom's up, I guess." Taking the jar from Tsukishima, Kuroo pinched his nose and swallowed as much of the Polyjuice as he could in one go. "UGH. It's like chewing on a quaffle. A used qu—"
Kuroo's voice cut off with a squeak, and Tsukishima looked away, not especially wanting to watch the transformation. A tense few seconds followed where Kuroo made breathless noises of pain, and Tsukishima wanted desperately to look but refused to in case Kuroo had done something horrible to himself.
"Okay, I'm decent," Kuroo said, although with Fujiwara's voice. Tsukishima turned back, and his retort got stuck somewhere in the back of his throat.
Because Kuroo looked mostly like Fujiwara, but not identical. More like a sister, with the same sharp nose and freckled shoulders, but if Fujiwara's sister somehow had Kuroo's eyes and cowlick.
"What did you do?!" Tsukishima gasped, angry because he already knew exactly what Kuroo had done, and fucking around with potions was dangerous, dammit. He punched Kuroo in the shoulder, hard. "You moron!"
"Two of her hairs, one of mine," Kuroo shrugged, but she looked a little sheepish. "I figured it couldn't backfire that badly since we already kind of look alike. C'mon, don't be mad. You don't really want to fuck Fujiwara, right? This is pretty close to what girl me would look like, probably. What do you think?"
Tsukishima looked her over critically. He preferred regular Kuroo, definitely, but like this she was still athletic and well-muscled, dark hair still sticking out all over but falling past her shoulders. She had more of a waist than Tsukishima had ever suspected under Fujiwara's Quidditch robes, and pretty nice breasts, actually. There was just enough Kuroo in her face that Tsukishima found it more appealing than he'd been worried he might. He still side-stepped the question. "How does it feel?"
"Different. These are surprisingly nice." Kuroo cupped her breasts in both hands, pinching her nipples, which were cutely dark. "Oh. Hey, feel this."
Kuroo grabbed Tsukishima's hand and covered one of her breasts with it. Tsukishima wasn't a breast man by any stretch of the imagination, but when he ran his thumb over Kuroo's nipple, already drawing tight, Kuroo made another noise that Tsukishima liked a lot.
Kuroo tugged Tsukishima down, lying on their sides, and Tsukishima relaxed into the kissing once his eyes were closed. She was a little curvier and breathier, but Kuroo's lips were still chapped from broom-flying and her hands still slid down to squeeze Tsukishima's ass the same way, so it wasn't as hard to get into it as Tsukishima had thought. He didn't tense up until Kuroo pushed one of his hands between her legs.
"Do something already," Kuroo ordered, squirming. She was flushed, eyes bright, when Tsukishima opened his eyes, and already slick where Tsukishima's fingers were just skimming the outside.
"I don't know what to do," Tsukishima stalled. Kuroo pushed two of Tsukishima's fingers inside her, tight and hot around them.
"That, do that," she panted, pushing down against them.
It took a few minutes for them to figure out how to do it more successfully, how to work together instead of being distractions. Kuroo laughed that it was a lot easier to find his own clitoris than somebody else's, and Tsukishima thrust his hand a little more roughly, eyes narrowed at the idea of Kuroo doing this to somebody else. It turned out Kuroo liked it deeper, rougher like that, though, so he kept doing it until she came, squeezing tight around his fingers and shuddering. If possible, she was louder as a girl, and Tsukishima shivered himself at the echo of her moans off the stone walls.
"Should I stop?" Tsukishima asked, not sure what to do with his hand, not sure if the little continuous noises Kuroo was making every time he curled his fingers was encouragement or overstimulation.
"Inside me," Kuroo panted, kicking at Tsukishima's thigh. "Now."
"Now? But you just—"
"NOW," Kuroo repeated, reaching down to do it herself, pushing Tsukishima's hand out of the way and tugging him over her, curling legs around the backs of his thighs to try and pull him into the right spot. "Come on, just do it, come on."
"Okay, okay!" Tsukishima said, feeling nettled in spite of everything. He reached down to position himself more successfully and pushed inside. Kuroo groaned, digging fingers into Tsukishima's upper arms, and it sounded both pleased and relieved. It was sort of the same as fucking Kuroo normally and sort of intensely different, much easier to start, the pitch of Kuroo's desperation definitely new. "Is it that different?"
"Yeah, it's all…" Kuroo arched her back. "Mm. Like aftershocks but so good." Kuroo rolled her hips up, trying to get Tsukshima to move. "Like if you did it just right I might come again."
"Fat chance of that," Tsukishima grumbled, feeling totally out of his depth and mostly just trying not to come himself. He glanced over at the hourglass. "Like twenty minutes left."
"Don't watch that thing." Kuroo laughed, sliding her hands down to Tsukishima's hips, trying to show him how she wanted him to move. "Mmm. Hey, wait a sec, let me roll over."
If Kuroo was a sight on her back, on her hands knees she was like pornography incarnate, and that was before she spread her knees a little wider to take Tsukishima in exactly right. Forget anybody else in Slytherin hearing her, Tsukishima hoped there wasn't anybody left in Ravenclaw Tower either.
"Not gonna last," Tsukishima warned, having no success trying to slow Kuroo down by gripping her hips tighter.
"Wait, wait," Kuroo gasped, dropping to her elbows so she could reach between her legs. Tsukishima groaned through gritted teeth as Kuroo's body gripped him somehow even tighter, almost possessively.
"I'm going to die, Tetsurou!" Unable to hold back, Tsukishima came, digging his fingers hard into Kuroo's hips and struggling to keep moving for Kuroo's sake. He thought she might have come a few seconds after him, based solely on the noise level.
Kuroo flopped on her stomach, and when Tsukishima collapsed on his side, she rolled over to curl up with him, their stomachs sticky where Tsukishima's softening cock was trapped between them.
"I'd be Tetsuko right now, wouldn't I? Oh man, Tsukki, you have to try this," Kuroo purred, rubbing against him. Kuroo was always a post-sex cuddler, but the cuddling wasn't usually this aggressive.
"Fuck, give me a minute, you incubus," Tsukishima panted. "And I'm not calling you that. Wait, is an incubus or a succubus the girl version?"
"And people say you're smart," Kuroo purred, running her hand through Tsukishima's mussed hair.
"Shut up, you just destroyed my brain with hetero sex."
"I can definitely fix that," Kuroo promised, looking gleeful. Tsukishima groaned.
His own Polyjuice potion tasted like he was licking a library book somehow scented with jasmine, which Tsukishima did not recommend. After the unpleasantness of the transformation wore off, Tsukishima opened her eyes to find Kuroo looking her over with consideration.
"Well?" he asked.
"It's pretty cute. But I'm glad you kept this." Kuroo leaned in to kiss the tip of Tsukishima's nose. Her hand came up to brush the scatter of beauty marks stretched across Tsukishima's shoulder. "And these. I really like these."
"Whatever," Tsukishima said, flushing pink. "Maybe focus on the parts you spent all that time making a potion for."
Laughing, Kuroo said he planned to, and then shoved Tsukishima onto her back. Tsukishima let her explore all she wanted, biting her lip and turning her head away when Kuroo discovered that Tsukishima's nipples were clearly more sensitive than her own.
"Mmm, so cute," Kuroo murmured, sucking on one nipple until it was drawn and tight against his lips while pinching the other, then switching sides. Tsukishima squirmed, trying to get Kuroo to do something else, anything, without really knowing what that something else was.
Seemed like Kuroo knew, though, because she smirked knowingly as she slid a knee up between Tsukishima's thighs, high enough to let her grind down against it. Tsukishima moaned before she could stop herself, definitely louder than she usually was, and the flush spread the entire way down her chest.
"Damn, if I were a worse potion brewer, I could get my dick inside you a lot sooner," Kuroo said, making Tsukishima give her a ruffled glare. She ran her palm down Tsukishima's stomach, lower until her fingers were brushing the inside of Tsukishima's thigh. When Tsukishima didn't stop her, she teased at the edge of Tsukishima's labia before pushing on finger inside. "Damn, you know I totally want to go again already? How do girls not just stay in bed and do this endlessly?"
"Why won't you stop talking?" Tsukishima groaned, throwing her head back.
Kuroo's solution to that, of course, was to crawl down between Tsukishima's legs and eat her out until Tsukishima was a trembling mess, so close all her nerves were stretched thin and tight with it.
"Aren't you gonna touch yourself?" Kuroo asked, lifting her head just far enough to grin at Tsukishima. He gave Tsukishima a teasing lick. "Like kinda here. Like I said, easier to figure out on yourself."
"You know what you're doing, just do it," Tsukishima growled.
"Well, okay, if it's a challenge," Kuroo purred. She could have done it faster herself, the flickering pressure of Kuroo's tongue perpetually just barely not firm enough or too much to one side or the other, but the delay of Tsukishima's orgasm just made it more debilitating in the end. The hot rush of it was in an entirely different place than Tsukishima was used to, deeper inside and pulsing, and when it ebbed a little, she realized she had Kuroo's hair in a grip that had to be painful.
"Sorry," Tsukishima murmured, working her fingertips down to Kuroo's scalp and rubbing in little circles to sooth the sting. "You have a lot more to grab this way."
"I kind of liked it," Kuroo said. Her fingers were still inside Tsukishima, and every time she moved them, warm ripples spread out, through Tsukishima's abdomen. "Also I want to come ridiculously badly, so please tell me you want to return this favor."
"I doubt I'll be any good at it," Tsukishima muttered. Kuroo was already crawling up her and gathering her in tightly, shaking under Tsukishima's hands.
"It is not gonna matter, trust me," Kuroo told her in between messy kisses that tasted like Tsukishima must taste, she supposed.
Kuroo tasted different, saltier and muskier and thankfully nothing like a quaffle. It wasn't a thing she wanted as a Bertie Bott's flavor, but Tsukishima decided it was tolerable in exchange for having Kuroo whine and squirm underneath him. Kuroo also seemed easier to get off than Tsukishima, same as in their regular bodies, which Tsukishima didn't mind either.
Kuroo's potion gave out somewhere after the third time they'd reset the hourglass ("For science," Kuroo had muttered against Tsukishima's breast). Despite the fact that he had come more times than Tsukishima both overall and in the last hour, it turned out that reverting back to your original body from Polyjuice was a little like hitting the reset button, so far as sex went.
"Awesome," Kuroo said. "Because I don't mind tell you I was little worried I wouldn't be able to get it up again for a week, much less in time to fuck girl you. I guess the old Nimbus 4000 can't be tired if I just regrew it, right?"
"Ugh, don't call it that," Tsukishima groaned. She was just relieved Kuroo's face was back to normal with no apparent side effects, along with his shoulders, Adam's apple, pectorals, and ass. And his Nimbus 4000 too, Tsukishima supposed.
"You okay to go?" Kuroo asked, sliding his palm down Tsukishima's side from ribs to hip and back again, the touch warm and soothing. The broom calluses were the same, but his hand was bigger this way, and Tsukishima was glad those were back to normal too. "It's fine if you had enough. Or if you just don't want to."
Tsukishima snorted. "Ten minutes ago you were trying to get me to bet with you over how many more times you could do it."
"Well, yeah, but," Kuroo shrugged, "it's a little different? So we don't have to."
Tsukishima digested that for a second, trying to decide how to respond. "It's sweet you're trying to respect the fact that this girl thing is basically all for you, but you know? Me being fucked as a girl doesn't on my end feel that different than you fucking me as a guy. The proper place for this concern would have been hours ago, when you were the first girl that I ever fucked."
"Oh, shit," Kuroo said, eyebrows rising. "Shit, Kei, I'm really sorry, I thought about all this other stuff, but honestly I didn't think about it like that at all."
"It's fine," Tsukishima said, uncomfortable as always while talking about feelings. "It's you. And you did ask, kind of. Well, at the beginning. Listen, can we just do it already? I'm here and you're here and your dick is back, so let's make the most of it. How do you want me?"
"Whatever," Kuroo said in a rush, hugging Tsukishima tightly. "It's all good. On hands and knees was really good. But I can't kiss you that way."
"Here, like this," Tsukishima suggested, pushing Kuroo more up against the pillows. He got it after a second, sitting up against his headboard and Tsukishima climbing into his lap. Tsukishima liked how Kuroo's hands settled naturally on her hips, and how Kuroo might be able to suck on her breasts this way if she sat up a little. "Yeah?"
"Yeah," Kuroo agreed, tugging down Tsukishima's head to kiss her. Tsukishima let Kuroo kiss and stroke hands down her back as long as he wanted, not feeling any rush about it since they had a whole hour before he changed back. "Mmm, tell me when."
Tsukishima let the warmth in her stomach build up before finally saying, "Now," and Kuroo looked relieved, which probably had something to do with how Tsukishima had been rocking lightly on top of his dick for that length of time. It was different, having Kuroo slide inside him as a girl, but on top like this Tsukishima could control how fast and how deep, and it was fine.
She could control the whole thing like this, she realized, using Kuroo's shoulders for balance as she pushed up on her knees a little and then slid back down.
"Ohh," Kuroo said quietly, apparently having the same realization. Grin spreading across his face, Kuroo relaxed back against the headboard just a little more comfortably. "Oh yeah. Go for it."
Tsukishima did, circling her hips just right until it sent goosebumps down her arms, until Kuroo slid one hand down from her waist to thumb at her clit. Tsukishima came apart in a clenching, shuddering wave and collapsed against Kuroo's chest, moaning sharply as Kuroo made her bounce chasing his own release.
"I'm so done," Tsukishima groaned when they were spooned on their sides. She slapped weakly at Kuroo's hand where he was still cupping her breast, rubbing his thumb over her nipple "Stop that."
"They fit perfectly in my hand, though," Kuroo said, like that was some kind of excuse, and then nibbled on the curve of Tsukishima's neck to turn her grumbling into a sigh. Tsukishima forgave him, though, because when he uncurled from his ball of transformation misery as his normal self, Kuroo looked just as relieved as Tsukishima felt.
"What are you gonna do with the rest of the potion?" Tsukishima asked idly while Kuroo was busy kissing all the parts of Tsukishima that he was glad to see again.
"Dunno," Kuroo lifted his head from Tsukishima's pectoral. "Give it to Bo? He'll use it for way better pranks than me."
Tsukishima raised an eyebrow. "You're not saving it to do this again?"
"Nah." Kuroo's grin was soft around the edges, eyes fond. "It was pretty awesome, but I'd rather look at you than Tanimiya any day. It's cool we could try the other combinations. But it just proved this one is the best one, right?"
"Well." Tsukishima tried to keep a straight face, but the smile leaked out anyway. "You already know I prefer the Nimbus 4000 version. And you'd probably have to upgrade to something sturdier to keep up with my girl stamina anyway."
"I know, right?!" Kuroo agreed, going limp against Tsukishima's chest. "I'm exhausted! Who the hell taught you to be such a sex fiend?"
"An incubus," Tsukishima answered, winding his hand in Kuroo's hair and giving it a yank. "A deviant incubus with terrible hair."
"There's no mirrors in hell, Tsukki," Kuroo mumbled, clearly already falling asleep.
Tsukishima felt the sorest and grossest he'd ever felt in his entire life, but somehow he stayed right there in Kuroo's bed, dozing on and off until Kenma eventually came into the room to see if they'd died.
"I brought you food and butterbeer," Kenma said, entirely unruffled by their nudity, immune over long exposure to Kuroo. Tsukishima on the other hand, tried to roll himself in the sheet and only ended up on his stomach gasping for air as every abdominal muscle he had seized in agony. "I'll give it to you in exchange for the promise that under no circumstances will you use the rest of the Polyjuice on Lev."
"Deal," Kuroo agreed, sitting up to grab Kenma's bag. He stuffed half a Pumpkin Pasty in his mouth before adding, "We've been thinking Bokuto."
"Ugh," Kenma rolled his eyes before looking back down at Tsukishima. "No wonder you wanted to turn him into somebody else."
"It didn't help," Tsukishima sighed, then grunted when Kuroo slapped his ass affectionately.