okay so it was actually kinda sweet, the snippet of it i saw in my head. because I hc Sirius as the one who usually tops, and I think in this world James hadn't worn the strap before. but in this moment, James is riding Sirius and looks down at him and is so fucking overcome with how much he loves him that he's like, i have to know what it feels like to be inside of him. so he tells him that - 'i want to fuck you,' all breathless and sure - and Sirius is surprised only for a moment, asks, 'yeah?' as a grin slides on his face and his brow lifts, because he's already so turned on at the idea. and James says, 'yeah. give me that,' as he shifts off of him, leans up on his knees and watches Sirius remove the strap, both of them staring at each other as he does so. James fumbles a bit putting it on himself, but as soon as he's got it he's on top of Sirius again, and he can't help but moan, 'fuck,' just at the thought of what he's about to do, because Sirius is spreading himself and guiding James towards his entrance and when James watches Sirius's hand wrap around the strap, already slick with his own fluids, he swears he can feel it, and he has no idea how he hasn't asked to do this before now, because he's suddenly starving to see the look on Sirius's face when he enters him.
and that's it (: for now (: but I think there needs to be a WHOLE lot more dirty talk about their shared cock and how James wears it so well (his praise kink remains just as present when he's topping, he learns)