NTR is a genre focused on infidelity, specifically where a protagonist’s partner is "taken" or seduced by another person. In this specific keyword context, the appeal (for the intended audience) lies in the . By taking a character who is defined by her absolute loyalty and domestic perfection and placing her in a situation of betrayal, the story creates a high-stakes emotional and psychological conflict. Yamato Nadeshiko - TV Tropes
However, I can offer a literary/anime trope explanation if that would be helpful: yamato nadeshiko ntr tekikoku no otoko ni daka