Remus is Seme
Sirius wanted to give Remus a bath.
It was just one of those things on his BucketList.
And after all, Remus was a dog too. Er-sort of.
And Sirius figured that Remus should enjoy it as much as he did.
So Sirius got everything ready in the bathroom, went outside, and kidnapped his favorite man. (Most people thought that he and James were best friends, and they were, in a way, but at the moment, James was way focused on Snape, and Sirius was giving him space. And hoes before bros in this case.)
"Sirius, where are we going?"
"You'll find out in a minute. Hush up."
Sirius whispered a password and they stepped inside.
"Padfoot, are we in the prefects' bathroom?"
"…Yeah."
"Why?"
Sirius let go of Remus to let him see the abundant bubbles and the candles, along with some girly looking bath wash and a scrub brush.
"What are you-"
He cut off with a yelp as he felt Sirius slipping off his shirt and stood there in horror as Sirius removed his jeans and boxers and pushed the now naked Remus into the bathtub before removing his own clothes and jumping in.
As Sirius grabbed the scrub brush and coated it with body wash, Remus yelped again and shot out of the bathtub, Sirius followed him, and they sprinted around the tub a couple of times before Remus jumped back in, making his light hair dark.
Sirius thought he looked incredibly sexy and leapt in after him.
From outside the bathroom where two girls listening, one with long light hair and one with short dark hair, they heard some pretty interesting things.
"No! Stop it! Don't touch me there, Padfoot!"
"Moony, you know you like it!"
*splash*
"And you thought that you were in charge!"
Back inside the bathroom, Remus had Sirius pinned to the side and was scrubbing him with the scrub brush.
Sirius was in hysterics, and Remus was grinning devilishly, but was blushing too. It was cute and stuff.
After all, he was scrubbing his naked best friend in a bathtub while he was also naked.
It was fantastic.
"Moony?"
"Yes, Padfoot?"
"Well, I was just wondering…"
"Just say it."
Sirius said nothing. Remus was just about to ask and had his mouth open when Sirius leaned forward and kissed him. With Moony's jaw as low as it was, it was easy to take over and explore his best friend's mouth.
Then Remus regained use of his body.
The two girls outside were crying with mirth when they heard, "NO! I AM SEME!"