
This is a long shot. But a looong time ago I read a oneshot manga where I think Uke wakes up in a room or before getting to the room (Japanese style) of a yakuza leader being told he will be his partner from now own. There is some bdsm involved. I think it was a one shot attached like an extra to another main story not related to it. I remember the last page was the Seme and uke (who accepted his role) walking with kimono looking like a freaking portrain and the yakuza goons beside them. If this ring a bell let me know.
Can this be it?
https://www.mangago.zone/read-manga/muri_marriage/
Did the girl really make the beta conclude “kill ja heon but not get in lord mugos nerve”? If that was her conclusion as well then she is not as smart as I thought.