I don't enjoy NTR and cheating manga, but the idea of having bad choices in romance and marriage is a valid drama plotline, and without resorting to time travel like the k.manhwas, I kind of want to read a serious isekai where MC isn't some ethics saint or harem king and failed in marriage then gets a happy ever after.
That being said, anyone expecting/hoping something plot worthy in this manga should not expect it, because this is pretty trashy and exactly the kind of manga people who dislike cheating avoid. This isn't netorare (other guys stealing protagonist's loved one) because the feeling of jealousy/negative needs to be invoked. This might be netori (MC steals other character's loved one) but netori is also associated with stealing, and since the target character (not the stolen girl, the guy) is not around, I don't think it's netori.