So it might be a little bit late (actually VERY late) since this prompt has been over a month, but I have finally finished it yayyyyy so I'm gonna post it anyway
Prompt: Body Swap AU - @wolfstarmicrofic
WC: 768 words
(there's a tiny hint of Jegulus in this one, so if this ship is not your cup of tea, feel free to skip!)
Sirius's day had been exhausting.
It was not an easy day to begin with, since he was technically "Regulus" for today.
Long story short, a spell gone wrong when they were trying to "communicate as brothers do" (and obviously failed), and the next thing they knew, they swapped bodies. After Regulus (who was now "Sirius") went through every spellbook he could find, he found out that the spell would wear off after a day.
They thought spending a day being one another should be easy, which was why they agreed not to tell anyone.
They were wrong.
Regulus told Sirius to act mean if he didn't know what to do, and not to talk too much. So Sirius glared at anyone who looked in his direction, and he answered questions within three words. He thought he was doing a great job, but Regulus's friends proved him wrong again.
Regulus had specifically warned Sirius about Barty, saying he could not be too mean to him. He didn't think it could be an issue until it did. Unwillingly, Sirius had now learned that Barty had a degradation kink the hard way.
Finally, in the evening, he managed to escape from a slightly aroused Barty by using Reg's prefect rounds as an excuse; he had never been this grateful that his brother was a prefect of Slytherin.
There were even tears in his eyes when the familiar lanky figure of his friend came into view. It made Sirius giddy that his partner today was Remus.
But he could still feel that this Remus was not the one Sirius knew. Something in Remus's eyes remained distant, and the smile was too polite, which was, in fact, a good thing, reminding Sirius of who he was, so that he wouldn't pounce on Moony the first thing as he approached his friend.
"Evening, Regulus." Merlin, did Remus's voice always sound so endearing? Or was Sirius just tired?
"Evening."
"Shall we begin?" Remus gestured towards the hallway, and Sirius nodded.
They strolled through the third floor of the castle, catching some students who lingered outside their dorms. Sirius found out that with one "Regulus's look," he could make almost anyone behave immediately. He didn't even have to talk. It was quite satisfying, actually.
As they sent a couple from Hufflepuff back to their dorm, Remus started sighing, "You know what, I know you hate talking about your brother, but… I think he's acting a bit weird today."
Sirius's heart skipped a beat. Did he find out?
"What do you mean?" He tried to keep a straight face as he panicked internally.
"I don't know, he's… lacking energy today? And well," Remus glanced at Sirius with a weird look, "he, um, he seems to be avoiding James. Whenever James tried to talk to him, he just ignored him."
Regulus did what?! Sirius was doing his best to school his expression, but he stumbled a little as he thought about this.
Remus didn't seem to notice it. "Maybe they had a fight that I didn't know. Should I be concerned?"
"I'm sure 'Sirius' is fine. He should be normal tomorrow." Sirius blurted out.
"You know I can't help it. Worry about him, I mean."
Sirius glanced at him, confused, "Why?"
A small smile crept up to the corners of Remus's lips, his expression softened, and suddenly, this Remus was the one Sirius knew, the one he was most familiar with.
And Sirius felt like he realized something, something he didn't have a name for, but it was there, waiting for him to notice for a long time. It was all hidden in Remus's secret little smile, the one reserved for him, for Sirius.
Warmth crawled onto his cheeks. Sirius tried to turn his face to hide his blush, but it was too late.
"Regulus?" Remus asked, furrowing his brow, the smile gone, "You look red, are you not feeling well?"
Sirius cursed his (and his brother's) inherently pale skin. "Erm, yeah, something might come down on me earlier, so can we just, you know, end this round already?"
"Alright. Of course." Remus nodded at him, "Get some rest, then."
"Thanks, Moo- uh, Rem- I-I mean, thanks, Lupin."
Sirius tried very hard not to look like he was fleeing and walked towards the Slytherin dorm as fast as he could.
Luckily, all of Regulus's roommates had already fallen asleep, so he didn't have to deal with them any longer.
Sirius buried himself in an unfamiliar bed, thinking about Remus's eyes when he smiles, falling into a deep, sound sleep.
He couldn't wait for this day to be over.
