I was reading this in Korean out of morbid curiosity, and I have to say, I don't know what the hell the author was trying to do. He was going for a racial angle based on one cover he did, but then it turns out Noona will literally fuck ANY man (as long as he is not Korean). She was perfectly fine with fucking the brother's friends, one of whom was the whitest white man in Korea (a ginger) who also had a massive dong.
Then, the daughter was supposed to have some tragic backstory with her dad, but that was dropped. Next, she had a tragic backstory with her Korean boyfriend, which was also added out of nowhere. It is never explained how the mother, who left her husband because he was an abusive gambler, found her new husband. Or how the mother started fucking his son. Or how the mother is perfectly fine with her new husband and son both fucking her daughter and herself.
It is also bizarre how the wife left an abusive husband just to become the sex slave of an abusive father-and-son combo who do things like force them to drink alcohol with their asses, force them to suck cock while driving, step on them, spit on/in them, fuck them whenever and wherever the husband or son feels like it, and just generally treat the mother and daughter as literal sex slaves or pets, constantly dehumanizing them. Don't get me wrong, all that shit is hot; I just wish the author hadn't wasted entire chapters on pointless backstories, or that he had actually expanded on them properly instead of doing whatever it is he did.