Rei sleeps over Nagisa’s house, wakes up during the night, and goes from ‘ah, what a comfortable futon, i should really compliment Nagisa’s mother on her excellent taste in bedding’ to ‘HOLY SHIT I’M GONNA PISS MY FUCKING PANTS’ instantly. his mad scramble to get out of bed knocks blankets and pillows everywhere. he makes it to his feet, jams a hand into his crotch (and that wetness is totally sweat, yep), and runs for the toilet.
except, since Rei has the world’s shittiest luck, there’s someone in there. it’s ridiculous o’clock and everyone should be asleep and the ONLY TOILET in Nagisa’s house is occupied and Rei’s hand is wet. his bladder, so full it’s bulging against the waistband of his pajama pants, throbs and suddenly liquid starts dribbling down Rei’s leg.
Rei is a lot of things, but the sort of guy who’d piss himself in the hallway in front of the toilet? NOPE. so he sprints back to Nagisa’s bedroom, shuts the door, looks around frantically - no empty bottles, no containers, god dammit why did he help Nagisa tidy up his bedroom before bed?! he himself had thrown out three things that could’ve served as a makeshift toilet.
he’s out of time. little spurts keep leaking into his underwear. at the last minute, before he condemns himself to a very embarrassing accident, an idea strikes. Rei grabs one of the blankets from his futon, wads it up, squats down, and shoves it against his crotch just as the dam bursts.
so it’s humiliating enough that he’s crouched there in the middle of Nagisa’s bedroom, peeing uncontrollably into a blanket that quickly gets heavier in Rei’s hands as it soaks up his urine, soggy pants sticking to his skin… and then he happens to glance up as he lets out a sigh of relief and realizes Nagisa is wide awake and staring at him.
Rei squeaks, flails, drops the blanket, tips over and falls on his butt, still urinating (all over the floor, now). Nagisa sits up and rubs his eyes. ”Rei-chan,” he yawns, “what are you doing?”
there is really no explanation good enough, so Rei stutters incoherently for a while. ”i had to go!” he finally blurts.
"i see that," Nagisa says, sliding down off the bed. he picks up the sodden blanket by a corner, looks at it for a moment, then uses the driest parts to soak up the puddle on the floor. intensely ashamed, Rei just sits there and tries not too look at him… until suddenly Nagisa’s rubbing the blanket against the wet fabric of Rei’s pajamas and getting WAY too close to certain sensitive areas and when Rei manages to demand to know what he’s doing, Nagisa chirps, "cleaning you up, silly!"
and then he moves in, plops down in Rei’s lap, casually gropes Rei’s dick through two layers of piss-soaked material, and whispers, “but naughty little boys who pee on things they shouldn’t need to be punished.”
they don’t get much more sleep that night.