A shoulder to cry on becomes a dick to ride on...
This had a drama vibe, semi realistic.
Main guy at the start had just broke up with glasses, or their relationship was in trouble, he befreinded shortie and for some reason visited her at home, she liked him and was able to tempt him, they made love and then for some reason glasses appeared and showed she stil lloved him, then they gone back and forth.
I don't blame the guy friend shortie had like a normal NTR, she realized they other 2 had something and it was rekindling, talked with a friend, got drunk, and they fucked.
Then on the beach they did it again and glasses slapped her because probably it was looking like she was doing it there just to hurt MC, that again, is almost reasonable, he did screw both of them and was undecided.
After that they fell out, shortie left the cafe and they didn't see each other for years, MC and glasses got together and I think decided it wasn't right to cut a good friendship, MC decided to visit her and discovered she had a kid, his kid, then he begged her to be allowed to step in, he is not a bad guy, is just that shit happened, and shortie probably felt like she would force him to break up with glasses.
MC after all wasn't given the possibility to choose, glasses maybe thought shortie fucked the other guy to force him to drop her.
Would have been interesting if MC impregnated both.

Anyway, rest in peace to the mangaka, he seems to have passed away in 2018, right after starting a new mainstream manga.

Base +10