It was a BL and the whole plot is an Isakai where the guy is actually really into BDSM and gets transported to a dark bl Novel but actually loves it and the ML finds out by spying on the cameras or something
Maybe this one? https://www.mangago.me/read-manga/secretary_jin_s_confinement_diary/
It was a BL and the whole plot is an Isakai where the guy is actually really into BDSM and gets transported to a dark bl Novel but actually loves it and the ML finds out by spying on the cameras or something