Ben wants to be punished for what he did to Poe. He thinks of it as the only way they're ever going to be able to move forward. And Poe hates to admit it but he's got a lot of lingering resentment and bitterness over everything. It starts out as a weirdly agreed upon physical assault and then somehow they end up kissing and it ends up being rough sex involving not very safe or sane use of pain - biting, hair pulling, scratching Ben up, possibly a lack of lube, maybe even some knifeplay. Ben is ashamed by how much he gets off on it but he deserves the parts he doesn't like, too, so he doesn't tell Poe to stop.

+ Awkward aftercare
++ They were childhood friends/crushes before Ben turned to the Dark Side
+++ They were not romantically or sexually involved as adults prior to fucking