It amuses me how people actually haven't read the story before rating and reviewing (not just on this site). I'll be clear: there isn't ANY NTR or cheating or even any other love interests.
But basically, the female lead has never actually had any romance or love in her relationships, and was to be frank, emotionally blackmailed (i.e. 'If you don't put out, I'll break up with you) in the past, so she doesn't really have a good concept of what a healthy relationship is. So she rather forcibly goes out with the MC (he still agreed), first out of shock that someone turns her down, but then later out of feelings.
Frankly, if you took out the part where she's had tons of sex in her life, this is incredibly pure, wholesome fluff. But haters are going to hate, so you end up with mixed reviews. The MC has some minor OCD issues, but approaches things with honesty. He has to grow as well in this relationship.
Hilariously enough, the MC's friend LITERALLY has the stock 'hentai rapist protagonist' design (eye covering bangs and all!) with a stupidly attractive black-haired girlfriend. If you only look at the pictures, it hilariously looks like the friend is a rapist and the girl he's going out with was NTRd or something. (That couldn't be further from the truth, she's very vocal and crass).
So yeah, give this a shot and form your own opinions.