Yeah that's what it is big time, people get really insecure about relationships which is an understandable reaction honestly, but there are some people take to a point where it's to their own detriment. I learned that the hard way, I been cheated on too and when that happened I did my best to fix things, but in the end I decided it was best to just cut things off because continuing with that wasn't worth the hardship. People have a hard time letting go. For me, this ntr stuff only really goes as fiction for me though. It's a vastly different feeling playing a silly game or reading some doujin than actually getting cheated on, the latter obviously hits harder and is more personal so I don't think I would really enjoy getting "ntr'd" in real life lol