Unlike a standard rival, the NTR antagonist does not want a fair fight. Their pleasure derives from seeing the protagonist lose . They are agents of chaos, often using psychological manipulation (gaslighting, blackmail, or simply superior sexual aggression). Their feeling is Satisfaction derived from degradation.
Whether you hate it or are morbidly fascinated by it, the Immoral Quartet teaches us one thing:
Previously the symbol of loyalty. The NTR narrative requires their corruption to be gradual, often rationalized through loneliness, neglect, or coercion. Their feeling is Cognitive Dissonance —simultaneously experiencing pleasure and profound shame.