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Masturbaing when you shared a room with your brother was a difficult task.
Osamu would usually take care of it in the shower or bathroom if need be, but some nights he just couldn't sleep.
Overwhelmed by an unquiet mind, hormones surging through his body, he would lay, breath held in his chest as he stroked himself in short slow motions, careful not to rock the bunk bed or let a sound slip past his lips.
Nights like this were rare, and he always got away with it, at least that's what he thought until a muffled moan echoed about the room, stopping his hand where it gripped his cock. His heart pounds in his chest as his mind races- that wasn't him, was it?
He tunes his ears and that's when he is sure. Soft crickles of fabric, low huffed breaths and the tell tale squick of wet skin rolling against a palm.
Atsumu was definately masturbaing. Osamu waits, frozen, painfully hard cock held in a tight fist.
His brother was touching himself, right above him.
With only a metre and a mattress between them, he listens and wonders, did Atsumu know he was jerking off too? Did he hear him? Was it a coincidence or was he touching himself because Osamu was?
His cheeks heat at the thought and suddenly Atsumu's soft breaths became overwhelming and a twisted, confused desire fills him up. His cock throbs and he blows out a long slow breath as he starts moving his hand again.
He strokes himself tentatively at first but as Atsumu's movements become more erratic and the bed begins to squeak under his ministrations, Osamu gives in.
He fists his cock hard and fast and he's barely able to bite back a moan when Atsumu comes with a strangled wail, the sound sending Osamu over the edge too.
He lies still, a blanket of guilt wrapping around him as the room falls into silence, and soon soft snores can be heard from the bunk above him. Osamu lies awake, listening to his brother breathing for what feels like hours, his mind abuzz with a million thoughts and fears.
When morning comes and Atsumu says absolutely nothing about the night before, the anxiety Osamu has been holding onto evaporates.
He thought maybe he was wrong, maybe Atsumu didn't hear him? Or maybe he was jerking off in his sleep? Was that even possible?
These theories would also evaporate when the next time he gives into temptation in the heat of the night, the same thing happens.
And it would continue happening, quickly becoming the norm. On nights Osamu couldn't sleep, he wouldn't even try to hide it, throwing the blanket from his body, yanking his shorts down and groaning at the way the air hit his burning length, he fucks his hand unashamedly, and Atsumu would do the same.
The taboo of it all, listening to someone during their most intimate and private moment, let alone your own brother getting off at the same time, only served to increase their shared arousal as their ragged breaths meld together, like a chorus sung to the melody of the creaking bunk bed.
Things would remain this way for some time, until one particular night.
Atsumu had slid down the ladder in the darkness and slipped quietly from the room, presumably to use the bathroom. While Osamu did enjoy their mutually voyueristic jerk off sessions, he was impatient and took the opportunity to rub one out.
He lifted his shirt tail and tucked it between his teeth, taking himself in hand and stroking, letting his other hand cup and massage his balls. Osamu moved his hips in time with his strokes, his gruff breaths dying in the fabric between his teeth.
When the door opened, he yelped, releasing his shirt from his mouth and tugging it down to hide his cock.
Atsumu said exactly nothing as he pressed the door closed behind him and Osamu rolled to face the wall, his face aflame with embarrassment.
"Fuck 'Tsumu," he grumbled, "thought you'd take longer."
There was no response, only soft footsteps before the mattress dipped behind him. Osamu's body felt as though it was made of stone, immediately heavy and unable to move.
His heart leapt into his throat as Atsumu lay down behind him, the back of his hips touching to his own.
Then he heard the snap of a waistband.
Holy shit. Osamu sucked in a shuddering breath as he felt Atsumu move, body rocking rhythmically as he masturbates, his elbow bumping his own.
He lays there as his entire body immolates, his cock twitching as precome drools from his slit, wetting and sticking his shirt to his cock and- fuck it-- Osamu grips his cock and thrusts into it.
Atsumu moans in response, fucking his own hand faster, matching Osamu's pace. A fleeting thought passes through Osamu's head, that maybe they'd really done it this time, that the line had already been blurred and now they were hurtling passed with no way of ever getting back- but Atsumu groans through a bitten lip, a groan that sounds suspiciously like his name and Osamu can barely think at all.
With every motion and sound from his brother spurring him on, every point of contact between them a live wire, Osamu flies over the edge, senselessly painting the wall with white ropes, one last breathy moan passing his lips.
Through the white noise filling his brain he hears Atsumu gasp, feels his body tense and shudder behind him as he peaks and spills.
Osamu was right when he thought they'd crossed a line, as things escalated exponentially.
From laying back to back, to side by side, then tangled in each other's arms, eyes squeezed shut, foreheads pressed together as they touched themselves.
With legs tangled, they filled each other with hot breaths and moans, each softly hissing at the occasional graze of their sensitive cockheads, ending always over each other, their come becoming hot lube for each other, sending jolts shooting up and down their respective spines.
Other times they sat, a phone balanced between them as they crossed arms, stroking the other to completion as increasingly filthy porn videos played on the small screen.
The final straw, perhaps, is the day they set up the phone facing themselves and recorded as they teased and pleased each other with skilled fingers.
Filming was the first time they kissed.
Osamu wasn't sure what inspired it, but as his brother spilled over his fist, the way he keened, hips jumping into the pleasure, he felt compelled as he leaned into him, brushing their lips together.
It was a shy, nervous thing at first but when Atsumu parted his lips in response, Osamu pushed his tongue inside, leaning his weight onto him until he fell back and Osamu lay on top of him, grinding into Atsumu's palm as they explored each other's mouths, sucking and nipping at each other hungrily.
Later Atsumu would complain that Osamu ruined the video, although they still watch it, but this time they are naked, pressed against one another, mouthing wherever they can reach, rutting their flushed cocks together, coming in time with Atsumu on the phone screen.