So in case you haven't figured it out from the description this manga is about netori not netorare. For those of you who have no idea what I'm talking about NTR is a sub genre of romance where a love interest is stolen from their previous lover, usually though sexual conquest. Now I'm sure some of you are thinking "wait isn't that just cheating or adultery?" Well the thing is unlike with in real life where the blame is logically placed on the cheater, NTR places the blame on the person they cheat with. The story is written so the cheater is seen as a helpless victim, unable to resist the lustful wiles of a predatory casanova.
Moving on NTR is an abbreviation of the word netorare, or the word netori. In netorare the protagonist is the person who loses their lover, or the lover who is being stolen, with the stealer being painted as the villain in the story. In contrast the protagonist of netori is the person stealing someone else's love interest. Generally people don't mind netori, but a huge amount of people absolutely hate netorare.