This is story #4 (thus far) in a new series, Unbalance. (Chronologically it's #4, it was the first written and is the first posted.)
Shiro hums, eyes glinting in the dark room, one hand sliding down Keith's chest, smearing through the sweat and come on his belly. He shivers under the touch. The metal hand is a firm, almost painful hold on Keith's hip - which is already bruised, at both sides, from Shiro's harsh grip as they fucked.
Then he rolls away, sits up, slides out of bed with a lazy, fluid stretch that flexes the powerful muscles of his scarred back and shoulders. Shiro's metal hand ruffles through his short hair and neatens his forelock as he turns his head, scarred face in profile to Keith. He licks his flesh fingers lightly, eyes half closed.
He moves away, face no longer visible, heading for-
Keith's throat closes up for a moment, and he pushes himself halfway into sitting up as his body twinges. He ignores it, looking towards the door, where Shiro is about to leave him. "Stay the night. Please." he begs, his voice cracking. "Stay with me."
He knows it's not really Shiro.
But as the strong figure pauses, and then returns, settling onto his bunk and lying flush against him, he doesn't care. He turns away, the broad body warm at his back.
Sharp teeth nip at his throat - too harsh, Shiro was always softer with his bites, almost gentle, even when their sex was rough - and Keith closes his eyes, tears welling up in them. The tears aren't for the sting of the fangs closing around his shoulder, pricking his skin.
Keith folds his arms together and holds them close against his chest, instinctive reaction to the hurt he feels. The body curling possessively around his own is familiar, though a little too warm, and Keith tries to fall asleep quickly enough to forget that it isn't truly the one he wants.
Kuro purrs.
Unbalance has an endgame happily ever after; in the meantime, buckle up children, it's going to be a bit of a rough ride.