Atsumu has always run cold, but this, he thinks, is a whole new level.
He knows that the wind whistling across the rooftop must be cold only because it’s nighttime in the peak of winter; even in nothing but a thin shirt, Atsumu feels nothing.
The click of the roof door opening behind him is as sharp as a firecracker to his newly enhanced senses. His ears strain for the tread he knows as well as his own, but catch nothing—Osamu moves silently these days, more than usual, a soundless prowl slipping into his gait when he forgets.
(Forget isn't the word. This isn't something one easily forgets, like leaving your gym shoes at home or skipping a meal from practises that run over-long. There's no forgetting allowed.)
A heat at his back is the first indication he gets when Osamu stops behind him. The second is the hair at the back of his neck tingling and every instinct in him coiling up and hissing,danger danger turn around attack—
Atsumu keeps his eyes fixed on the city skyline, knuckles clenched white in his lap. The night sky is mottled with clouds and smog, the waning moon hidden behind the pollution. After a moment, the heat moves away, and Osamu takes a seat on the edge of the roof. Atsumu flicks a glance at the gaping distance between them, and his lip curls. He runs his tongue over his teeth; the points are sharper than they were a minute ago, and the fact makes him squeeze his hands tighter.
They say nothing, only the sound of the wind howling between them. When it’s the two of them, it’s normally Atsumu who breaks the silence, but instead he turns his head a fraction, angling to observe Osamu.
There are dark smudges under Osamu's eyes, an exhaustion which bows the lines of his body under its weight. The shirt is fresh, but stripes of dirt peak out from under the collar of his shirt, along with darker streaks of—Atsumu inhales, confirms—dried blood.
Atsumu turns his head fully, wrinkling his nose. “You didn't shower?” he asks, incredulous.
Osamu lifts a shoulder in a half-shrug. “I crashed as soon as I got back. I just woke up.”
The first part is no surprise. Atsumu was up all night, a by-product of no longer requiring sleep. He'd heard the front door slip open, then shut, and the ragged breathing as Osamu dragged himself into their shared bedroom and collapsed into bed. The scent of blood had been fresher then, whatever prey Osamu had hunted down in the full moon reeking from his skin, and Atsumu had bitten down on his lips so hard that he pierced skin.
The blood was only a small part of the problem. Stronger still were the whispers that clawed at the edges of his mind, a sharp primal urge insisting that he lunged now while his guard was down, while his enemy was at his weakest, to sink fangs into the exposed line of his prey’s neck and tear—
Atsumu's lips were a ragged mess in the morning.
“Could've showered first before bringing your stench up here,” Atsumu says, without heat. He scoots closer, feet swinging against the concrete.
“You didn't shower either,” Osamu points out, because of course he could tell, and Atsumu laughs, brushing shoulders against his twin’s.
“I don't sweat anymore, so.”
“Disgusting,” Osamu says, and finally, finally relaxes his weight.
Atsumu smiles, and ignores the prick of fangs against his tattered lips.
If he thought it would work at all—if it could fix any of this—he would plunge his own hand into his cold, unmoving chest, and pull out the part which writhes and screams and recoils at the presence of his own twin—at Osamu, of all people—and crush it between his fingers.
(It wouldn't, though. All he would get would be a gaping chest and an expression on Osamu's face that he’d never wanted to see again.)
Osamu's shoulder is almost burning against Atsumu's side. Atsumu digs his fingers against his palm, and savours the feeling.