Never thought I would hate literally every single major character in a hentai doujin before but here we are. A shame too because I'm really digging the art style.
What is going on? So the guy gets her drunk and takes advantage. But he's also dating her friend? So she can't tell? But why was he beaten up if she's his gf?
The guy get college girl MC drunk and takes advantage of her. MC later find out guy is dating her sister who is also his coworker but doesn't say anything out of fear of making her sister unhappy. Some unconvincing flashbacks to MC's high school time explaining why she is the way she is. MC and guy fuck more. MC catches guy fucking another girl and getting beat up by the girl's BF. Guy then reveals that he had a good life which turned downhill since MC's sister joined his company and became more successful than him. He then started the relationship with MC's sister because she somehow became the only person who's still nice to him and he "loves" her for that, but at the same time he's also been sleeping around to get back at the sister for...ruining his life, I guess?