Bukly?
https://www.mangago.me/read-manga/danshiryou_no_omocha/
I srsly don't recommend this one coz it's dark,this one set on all boy high school(idk if it's a private sch or not) but yeah i'm having mental breakdown reading this..anyway, this is the only one i can think of when u said 'slave' π_π
this is it thank you! its so bad but it just started plaguing me a while ago, thank you!
Really?? have fun ^ω^
https://www.mangago.me/read-manga/caste_heaven/
Well... This one seems similar?
But it much more twisted....
i am ashamed im looking for this... but a manga where this guy goes to a private school and becomes a sort of ummm... slave to the other boys except his main bukly falls in love with him?