Kurt swallowed nervously, looking down at the vial in his hand. This was it. Once he drank the potion there would be no going back. The liquid was a light brown-gold colour and swished smoothly around the vial when Kurt shook it. Steeling himself, Kurt raised the potion to his lips and then drank it quickly. Immediately he felt like he’d swallowed firewhiskey and then he doubled over in pain, the fire spreading from his stomach to the rest of his limbs. His head felt three times too big as it shrank down, and his hair itched furiously as it turned dark and curly. His bones cracked and groaned as they were forced by the magic into a smaller frame.

Kurt was close to passing out when suddenly the pain stopped and he could stand again. He picked himself up from the floor-he couldn’t remember when he’d fallen-and then stumbled in the unfamiliar body. Well, calling it unfamiliar wasn’t exactly true. Kurt knew Blaine’s body possibly better than he knew his own but it was still hard to stand in a smaller body whose centre of balance was quite a bit lower than his own. He lifted his hand in front of his face and the breath whooshed out of him even though he’d been expecting the tan hand. The fingers were thicker than his own and the hair on the arm was coarser and darker.

Kurt took a few cautious steps then stopped when he was satisfied that he could walk in Blaine’s body. His clothes were about a size too big: something that caused warmth to burst out in Kurt’s stomach. He loved that his boyfriend was smaller than him, loved seeing him in Kurt’s clothes when the sleeves were too long and the pants nearly covered his toes. He turned to look at himself in the mirror and an indulgent smile broke out on his face when he saw how out of place Blaine looked in the too big skinny jeans and the sweater that was technically for women but Kurt could rock. Checking the time, he realised that he only had another fifty-five minutes before the potion ran out and he’d change back into himself. Kurt bit his-Blaine’s-lip then started shucking off his clothes quickly. Blue wasn’t Blaine’s colour anyway.

*

It had started out as an off-hand comment made by Blaine. Kurt had been fingering him when Blaine had moaned out “I wish I could show you how good it feels when you do that”. Well, it hadn’t been as well-articulated as that but the general feel of it had been the same. Kurt had pulled back, eyes wide, and told Blaine that that could be arranged.

The potion had taken a month to brew. A month full of Blaine showing Kurt how to touch him so that he would be able to make the most of his hour in Blaine’s body. A month full of hiding the cauldron from the professors and ignoring Santana’s persistent efforts to get him to tell her what was going on. The Slytherin was often his partner in crime when it came to sneaking in to the Hufflepuff common room to meet up with Blaine and Brittany and had wanted to know where he was going every night.

It was worth it, Kurt thought, to be able to do this now. The sight of Blaine’s body wasn’t new, but now that Kurt could make it flex and stare as much as he wanted it felt like he’d never seen it before. He ran his hand down Blaine’s abs and grinned when he relaxed and they disappeared. He fucking knew that Blaine tensed when Kurt was looking. Kurt reached a hand up and traced a finger around a nipple, teasing himself and shuddering at the feeling. Blaine wasn’t as sensitive as Kurt was but a low warmth was building in the pit of his stomach as he rubbed against his nipple.

He looked back up at the mirror and moaned at the sight in front of him. He knew that look. It was how Blaine looked after they’d been kissing for a while and he wanted more. Kurt’s bottom lip was wet and a little swollen from where he’d been biting it, and his eyes were bright. His cock was half-hard in the thatch of untrimmed hair-another new sensation, Kurt always maintained a certain level of neatness that Blaine could never be bothered to-and twitched when he looked at it. It was strangely arousing to feel how the blood rushed to his erection and the difference between how Blaine’s cock rose to fully hard and his own did.

He sucked his fingers into his mouth and licked around them, knowing exactly where was the most sensitive and actually gasping when he flicked his tongue against the tip of his index finger. His fingers now wet, he slid his hand down his chest to wrap gently around his cock. His mouth fell open at the feeling and he whined a little in the back of his throat. It felt so good but also so strange to feel his cock raise up higher than he was used to and press against his abdomen. Curious, Kurt pressed his dick against his stomach and closed his eyes against the sensation of hard muscle against the soft skin of his penis.

When he glanced at himself in the mirror again Kurt breathed out slowly, drinking in the way he looked, like Blaine did when he was close. He walked back slowly, enjoying being able to stare shamelessly at the way Blaine’s body worked. The shift of the skin over muscle in his legs as he walked, the way his chest expanded with every breath, the tendons in his neck that stood out when he clenched his jaw. Blaine was just so much more solid than Kurt was. Kurt could feel it in the way Blaine’s body moved, the way it automatically grounded itself. He felt like nothing could move him if he didn’t want to be moved and Merlin that turned him on.

He sat down on the bed and spread his legs, eyes watching the movement that Blaine’s body did instinctively. He took in everything from the tensing of Blaine’s abs and the way they framed his cock to the way his balls sat low and heavy above his hole. He looked away briefly to search for the lube, which he found easily next to his pillow, then turned back to watch himself as he squirted the lube onto his fingers. It was self-warming, a handy little charm that Kurt was always appreciative, but never more than now when he didn’t want to look away for a second more than was necessary.

Maybe it was messed up, what Kurt was doing, what Blaine was allowing him to do, but in the end it was all for Blaine. All so that Kurt knew how to take Blaine apart, knew exactly what it was he did to Blaine and really Kurt would do anything for Blaine and this wasn’t exactly a chore.

Kurt rubbed his fingers over his balls, shuddering at the sensation, then moved them down to circle his hole. In his own body Kurt wasn’t the biggest fan of being fingered. He wouldn’t turn it down if it was offered but it wasn’t on his list of top five things to do in bed with Blaine, which included blowjobs and fingering Blaine.

Touching himself now, Kurt felt as if his skin was on fire. The angle was awkward but already he was clenching around nothing, his body begging him to put his finger in and fill him. His eyes closed and he tipped his head back, breathing out harshly. He’d planned on taking it slow and teasing himself but now he knew what it felt like it was all he could do not to just fuck himself on three fingers at once and be done with it. Suddenly all the times Blaine had fallen apart before he’d even really been touched made a lot more sense to Kurt.

He pressed the tip of his finger in, more pushing at the rim than actually going inside, and bucked his hips forward at the feeling. He fell back down onto the bed and pressed as much of his finger in as he could. He was nearly at the second knuckle when the angle became too much and his arm twinged with pain. He pulled his finger out and flipped over onto his stomach and didn’t waste any time before reaching back and sliding his finger back in, fully this time. He rutted against the mattress in time with the thrusts of his finger in and out of himself.

Kurt had only been this turned on a few times in his life. It felt like he was both fingering Blaine and being fingered by him at the same time. He knew the feeling of Blaine’s ass clenching around his fingers just as he knew the broad feeling of them in his own ass. Deciding he was relaxed enough, Kurt added another finger and spread his legs even further. The result would have been an embarrassing position if he was in his own body, but when he looked over his shoulder at the mirror all he saw was his boyfriend spread out and looking so fucking wanton that he nearly came just like that. Instead he braced himself on his left hand, still pumping in and out with two fingers with his right hand, and twisted his body so that he could stare at himself in the mirror.

There was no hesitation in his body, no worry about looking silly or embarrassing himself. All Kurt wanted was to make Blaine’s body feel as good as possible and to have the incredible orgasm he could feel building.

Kurt wasn’t ready for three fingers, still too tight, but he ignored it and pressed three in at once, revelling in the burn. He cried out, the sound familiar to his ears but also warped by the way Blaine heard himself, and fell forward onto his elbow. His eyes were tightly shut as he worked himself over. He crooked his fingers a little, searching for that perfect spot and…there! He nearly screamed at the feeling, fucking forward into the mattress and rubbing himself shamelessly against it, not even bothering to lift himself up enough to thrust against it properly.

He thrust his fingers in and out rapidly, twisting them each time, trying to feel the liquid fire that came whenever he hit his prostate. After a few thrusts he managed to find it every time. He was letting out a steady stream of swears as he got closer and closer to coming.

Kurt panted against the mattress where his face was pressed against, so close but still just teetering on the edge when he had an idea. The thought had barely passed through his mind, just a feeling, really, when he pressed his fingers right against his prostate and cried out “Kurt”. The sound of his name in Blaine’s voice, so wrecked and turned on, sent him over the edge and spiralling into an intense orgasm. Everything went fuzzy around the edges and his head spun.

Kurt vaguely felt himself come in messy spurts against his chest and the sheets before his body relaxed against them. He pulled his fingers out of his ass, wincing at the pain now that he didn’t have pleasure to dull it. He rolled over onto his back away from the wet spot and slowly came back to himself. The thought crossed his mind that he should clean up but all he managed was a quick Scourgify before he fell asleep.

Kurt was woken up by the feeling of his body turning back into his own. He turned over onto his side and curled into a ball until it was done. Still tired, he had nearly fallen asleep again when he heard someone enter his room. He made a move to pull the covers over himself when he felt Blaine chuckle then climb into bed beside him.

“How was it?” He asked. Kurt just smiled and snuggled back against him.

“It was magical.” He replied, laughing when Blaine groaned at him. Kurt sighed happily at the feeling of Blaine’s body against his. It had been fun to inhabit Blaine’s body for a while but there was nothing quite like being held in Blaine’s arms.