Disclaimer: I do not own Bleach.
There are no feelings between them, unmistakably. In a perfect world there would be love… but this world was never fair to Abarai Renji. They're just two bodies melting into each other, hungry for touch, demanding and rough, fighting for dominance and selfishly needy. And he doesn't stop to wonder if things ought to be different, because it never did him any good to ponder things. At the end of the day, it simply feels good to be embraced by him, even if he doesn't care much, and to Renji it matters even less if it's him or somebody else. In the dark it's not even clear if it's him anyway. It could be someone else…
Maybe someone who cares… When he crushes his body against the other man, it makes his head spin to imagine, yes, just imagine that the other's touch is filled with love. That the fingers ghosting over his chest will want to stop above his heart and feel it beat madly and his pulse will also quicken. And that thought makes him lean more into his hand and allows a throaty groan to escape his lips. Although it's sort of hard to imagine it's not him, since his presence is overwhelming and fills the room, fills him, his world, body and spirit, he hovers above him, ascertaining his dominance. Every time he closes his eyes, losing himself under an imaginary lover with tender feelings, his captain brings him back with a rather violent flare of reiatsu, a frantic thrust or an unexpected gentle brush of lips against his sweaty brow. And it's definitely hard to ignore him, that cold bastard, he's so good at this! Renji grabs his shoulders and grinds lustily against his hips, urgently demanding, red locks of hair entwining with dark ones, and there comes the moment when he stops caring who the other is, because he is too focused on getting his own release, and he barely realizes that he holds him so tightly against his chest and the hands which tamed him into submission are gently caressing hot skin now.
So, yes, it could very well be someone else. Too bad it's not, that's the only thought in Renji's groggy mind early at dawn, when his captain leaves the bed and doesn't even bother to look at him, most likely disgusted, with him, with himself, who knows? It's not common of Kuchiki Byakuya to speak of his emotions. He vaguely realizes it's probably just as uncommon for Kuchiki Byakuya to spend entire nights in other beds than his own, but he dismisses that thought quickly, since he has no idea what to do with that.
There are no feelings between them, that is a fact. But apart, they each carry their own and Renji is fine with the "apart". There is no "together", there never should be. He doesn't ask for more than a warm bed once in a while and gets his wish fulfilled without having to ask. His captain must be really lonely for stooping down to his level, he thinks thoroughly amused, but that is his own problem, Renji does not care, he takes what he wants from this whole thing and is not bothered by being left behind. He does not want feelings, because that would be reaching for the moon and that's just foolish. That's why, whenever his vision becomes clouded and his world is filled and overwhelmed by a man who smells like cherry petals, he can slip away to a dream where there is something more. And for a few brief moments the moon is within reach.