>>723634571
the orthodox definition of netorare (true meaning of the word in Japanese dictionary) is simply cheating, so there has to be a romantic commitment being broken by the woman for it to be true, genuine, 100% bona fide 24-karat NTR. This is the granddaddy of the genre altogether.
However Japanese pornographic doujins have been applying NTR elements such as humiliation of the male protagonist to many stories where it's his mom, sister, a childhood friend he never confessed to, or someone he only admired from a very long distance like an idol. As a result of "if it quacks like a duck" logic, people just call all the doujins that play along the same exact 'degrading betrayal' formula NTR, and we can call this the colloquial NTR definition.
The common usage of NTR can thus be understood to be any story in which the male protagonist is emasculated by a female figure in his life having sex with strangers, which ironically is going to be nearly all of them, even acquaintances and random strangers he meets on the street. Common NTR can be summed up as "degrading betrayal" in general, an expression of the subconscious male desire to be doted upon by the women in his life, such as his mother, sister, and any friends he's made of the opposite sex, only to realize that these affections are fully negotiable and not at all eternal. Female fondness is reserved for those who provide what they all instinctively desire, be it money, safety (in a strong man who can protect them), and of course sexual stimulation.
What is missing from most NTR fiction in terms of accuracy to real life is that the man who does the cucking eventually gets bored of used up pussy and dumps her for the next beautiful young slut he sees. That's how real life goes.