Like Merrill said it's NTR C not the most common but it's still NTR
NTR or
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, (
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. 寝取られ, 寝(ne) as in 寝取られ means "sleep", in this case, "
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sleeping with someone (cheating)". 取られ(torare) is a noun coming from 取られる(torareru), "have something stolen/robbed".
It is a genre of anime (most commonly found in
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), with a specific idea at its centre - cheating. It has a (main) story where the protagonist has his/her lover stolen by someone. The sex in an Netorare hentai/NTR hentai will focus more on the couple that is having an affair together, rather than the married or dating couple whose relationship is being violated. Netorare/NTR usually has a female character as the one who is cheating on her husband or boyfriend, but it can also be a male character as well sleeping with other girls. Quite often, Netorare hentai/NTR hentai end in depressed,
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, and rage-filled characters rather than happy endings.
even in NTR manga that starts with it being rape or blackmail by the mid or end the other person is enjoying it and goes back to cheating out of their free will, there is no enjoyment coming from the LI in this story, so not NTR, just plain rape, I even researched the "NTR C" thing and found absolutely nothing, NTR is about jealousy if you are jealous of the rapist than your option doesn't matter to me at all.
edit: if you feel like your partner is a property then I care even less about your opinion