Does he even like her romantically? Can't be cucked if you didn't give a shit. He has 2 other options, and the highschool girl is still the worst possible choice for him.
She's got the most baggage, and the most sexual experience meaning past suitors he has to potentially deal with. She also has the least to offer emotionally. The other girls can be emotional support to him, but for the Highschool girl, he has to do all the work in the relationship. They've already proven this, his Kouhai was able to advise him on personal issues, and his Senpai got the highschool girl to think realistically about their situation and the future.
I'd personally be happy if she goes full yuri. As long as she's out of the running. I empathize with her as a character and want her to be happy but it's criminal how bad she is as a main heroine.
@bruhclone no. existentialism is just nihilism with sentimental icing. they are both empty relativism. i said what i said because it'd be telling the objective truth about how women are, and the manga is telling lies instead, though not quite as big as the commenters would like it to tell (-> to what extent this "rapist" is a moral monster for not respecting women enough)