AOB Japanese(?) BL/Yaoi pls help find

I think this story was a japanese manga. AOB, a group of guys find out their secondary genders (A,O or B). I think there's supposed to be some fated type pair thing with this. They reveal their genders in school rooftop I think. One of the guy friends (alpha) bites and rapes(?) MC (omega), although it happens later in the story after the reveal of their genders. ML(alpha?) who is also friends with MC beats up guy? MC and ML had already promised to be together or get married. Years pass. ML and MC are together, they're scientists or smth like that, and MC endures heats by themself or they're like painful or smth???? Tbh don't really remember the story. Do remember a bit where the friend who rapes MC sees MC later in life and regrets what he did. Turns out they were supposed to be fated pairs but bc he raped MC, MC doesn't love him and MC always loved ML.