I’d say it’s about the difference between NTR and swinging/polyamourous/open relationships. If everyone has sex with everyone, is it a world of NTR?
In the quote you are also ignoring the "designed to cause jealousy" part of the definition.
The sister isn’t sucking stranger’s dicks to cause jealously, she is doing it because she likes it. Likewise, the MC is not jealous of it. Same with the MomxSis scenes or the implied JanexEffi content. It’s the opposite, rather. I’m fairly sure Effi mentioning that Jane and John both taste the same is meant to be sexy.
It gets further into NTR territory with Hitomi’s scene, but even there, I’m not sure the scene is supposed to evoke jealousy. Hitomi is not a girlfriend. She’s just a random sexual encounter. At most she is a sexfriend. As far as I recall it is also less of a jealous "That’s my girl!" reaction and more of a extreme reaction to the unexpected situation. ("She deserves better!" is how the MC phrases if I recall correctly.)
I’d personally categorize the scene with the mother as NTR, because the following dialogue has some strong themes of humiliation. It’s a sex scene intentionally made to make the players feel bad and the MC feels betrayed. But even then, it is a bit ridiculous to call a wife having sex with her husband NTR. If anything, you, the MC, are cuckolding the father.
At least for me, the formula goes like this:
1) The Cuck has to feel entitled to the Stolen Lover. (Cannot just be a random person.)
2) The scenario has to feel like a betrayal of their relationship. (Cannot just find it hot and approve or be indifferent.)
It’s all about expectations. If you are the 20th person who fucks the town slut, it’s not NTR if there is a number 21. If you go to a prostitute, that’s also not NTR. If you go wife-swapping, that’s also not NTR. If you randomly fuck someone at the nude beach, it’s not NTR if that person then also fucks someone else. If you and your sister both have fun at the glory hole and then also (later) have sex with each other and each get another sex buddy, that’s not NTR. It’s just people having sex.
Of course that’s just my interpretation. It’s controversial enough that I decided to include examples in the FAQ instead of saying it definitely is or isn’t NTR.
Fuck. Yes. Christ am I sick of hearing people whining about "NTR!" without any actual understanding of
what it actually is, like morons bitching about their "free speech" being "censored" when they find themselves facing backlash for saying that all homosexuals should be burned at the stake.
NTR -that is, netorare, not to be confused with netori- is a
very specific fetish. It's about a character, almost universally a man, being shamed and humiliated by their partner being taken away from them by another to make them feel sexually inadequate. It is a
masochistic fetish, like being femdommed, tied up and whipped, or sissified, about taking taboo pleasure from something ostensibly horribly unpleasant and degrading, with the entire point here being the crushing feeling of shame and disgrace (usually compounded by the partner expressing how much better the sex is with the new lover to really rub it in, and the shameful feelings of arousal at seeing their partner being pleasured better than they could). Anything else is
not NTR.
It's very tiring having to listen to the endless whining by very thin-skinned snowflakes (another badly-misused term; a true "snowflake" isn't someone who dares to express offence at something that is intended to be offensive, but someone who melts the first time they don't get whatever triviality they want to go their way) about how "there's a female character in this game who is having sex with a character who ISN'T ME,
I'm being cucked arghhhhh!!!" I mean Christ almighty, how do these people even live with themselves?! Don't they realise that
at this very second there are millions of women all across the world having sex with
men who aren't them?! My GOD! How do they even watch porn without wanting to kill themselves in shame of being cucked so blatantly?