Before the war, some time after they get together, Steve finds out Bucky has a thing for getting gangbanged. After the initial jealousy, they talk it through and come to an arrangement: Bucky can go out and take all the dicks (maybe while Steve watches...and jerks off furiously), but only if at the end of the night, when Bucky’s a sloppy fucked-out wreck, Steve is the one who gets to go last, to finally stake his claim and fuck him, give him one final load to let him know who he belongs to.

Flash forward to post-WS, Steve and Bucky get captured by HYDRA. A trash party on Bucky ensues, (while Steve is forced to watch), etc etc, they escape. Cue horrible, filthy trash aftermath sex that maybe neither of them are really ready for, because - unlike all the other trash parties Bucky has been subjected to over the years - Steve’s here now, and Bucky needs Steve to remind him just who he belongs to.

Bonus: my trash kingdom for all the twisted parallels between the consensual and noncon scenes, e.g Steve (lovingly) dirty talking/slut-shaming Bucky versus HYDRA joking about how many fists the Asset can take, etc etc