Responses
I don't think this is the one you're looking for, but I thought of it while reading your description. Stars are a big part of it:
https://www.mangago.me/read-manga/my_roommate_obsesses_over_me/
ISNT THE ONE IM LOOKING FOR BUT THANK U SO MUCHHHHH AH
A manga where it was about a uke who had like blond hair and was a student or smth like that and he had a teacher or tutor(seme) who was helping him in the summer holidays and hes a sadist as well...?and i think the study was about stars as uke loved smth about the stars??? pls I randomly thought of this manga but I can't find it PLS HELP ╥﹏╥