A fetish in which someone close to the protagonist is either willingly or unwillingly seduced and stolen away. This isn't necessarily limited to one's lover, but may also include friends, unrequited love interests, or even relatives.
Closely related is netori/netoru (寝取り/寝取る). In this genre, the protagonist instead takes the lover of someone else. Also related is cuckolding, in which seeking out others is actively encouraged, even at the expense of the cuckold.
Posts on Danbooru should include the presence of the cheated on in some form, physical or otherwise (such as on the phone, as is common), or mentioned at some significant length. Do not apply this tag if only the artist's commentary mentioned that it was NTR-themed posts but other sign of it being such shown in the image itself (such as the "cuckholded" character being absent).
Not to be confused with cheating (relationship), which is when one party intentionally approached the third party without their partner's consent.
