There are times when he feels like the world's biggest fool. Giving and giving and giving, all for the low, low price of a scrap of affection. Sirius, of course, gives more than a scrap. Remus is, after all, his best mate. So Sirius kisses him and whispers sweet nothings in his ear and makes plans with him and laughs with him.
In those moments, he can almost forget it's not him, it's never been him. He's just the understudy, there by happenstance, always second best. The regular actor is too busy for the play, but Remus will never fully replace him, and everyone knows it.
There are glass shards going straight through his heart every time he remembers this. It always happens just when he's on the cusp of actually believing the fantasy he spun out of loose threads.
Sirius kisses gently at the spot behind his ears and runs his fingers not so gently through Remus's hair. His other hand is gripping Remus's hip tightly as he fucks into him hard and slow. The sounds coming from in between their bodies, the syrupy, foggy air, Sirius’s raspy exhales, his lips brushing against Remus's neck, Sirius’s body covering him, it's all driving him closer and closer until he can't take it any longer and cries out, fisting his cock. Sirius’s hand moves from tugging on his hair to covering his mouth, stifling his moans, and his cock drives into Remus faster now.
"God, you feel so good on my cock, you're amazing, you're fucking glorious," Sirius half-whispers, half-moans into his ear and Remus thinks he would have come again already if he could when he hears it. He's overstimulated and it hurts; he whimpers, his eyes rolling back into his head, but he can tell Sirius is so, so close, so it's fine. Almost there. Sirius lets out a loud groan as he stiffens behind him, balls deep in his arse, his right hand clutching Remus tightly enough for bruises to form.
"Fuck, James, fuck. Yes, Jamie. Fucking love you."
And there it is. Remus goes from fucked out and blissful to icy cold. As Sirius lets go and pulls out, his come dribbling out of Remus's arse, he feels more and more like the cheap whore he is and blinks back angry tears.
Sirius cleans them up with a couple of spells and they pull their jeans back up in silence. Remus is struck by an intense determination to break their whole thing off. He turns around and opens his mouth, fully intending to go through with it, but Sirius chooses the same moment to lean down and give him the sweetest kiss.
"Moony, that was fantastic, I really needed that," he smiles. "Come on, let's go back in before they try to come find us," he says and grabs Remus's hand, interlocking their fingers.
Remus swallows his words, smiles, and lets himself be dragged along.