Ummm idk I'm not sure but is it this one?
https://www.mangago.zone/read-manga/oblivious/
Nooo thank you tho!
Do-S Obake Ga Nekasetekurenai, perhaps
https://www.mangago.zone/read-manga/dos_obake_ga_nekasetekurenai/
Idk.. bout yaoi but i know a romance one with similar preface. Name free in dream world
YES THANK YOUUUU
YEA THANK YOUUU
If I remember correctly the seme was this guy who was in a coma, and he was basically able to like astral project in his ghost form and would like get freaky with this guy in his ghost form, not realizing that it wasn’t actually like a dream at first, and they didn’t even know each other. I think they only went to school together.