>>717773342
I get tired of typing this out.
Netorare is a japanese concept that specifically means to have someone important to you be stolen away emotionally, with aspects of humiliation and betrayal. It is not specifically about having an affair.
BSS NTR is a thing. The two characters aren't in a relationship, but the feelings are there, they simply haven't acted on them yet, and a third party steps in to steal one of them away, that's NTR.
Familial NTR exists. If you have a loving mother, sister, or daughter who starts dating this shady guy who treats them like crap and turns them against you, that's NTR.