Honestly, 'anti-NTR' as a search term always sends me on a bit of a tangent. It's less about a single genre and more about a reader's emotional intent—wanting that core relationship to be unshakable despite the world trying to rip it apart. The loyalty isn't passive; it's forged in fire. A novel that absolutely wrecked me in the best way was 'Marriage of Convenience' by Gu Tingfeng (translated title). It starts with a cold, transactional union, but the loyalty that develops isn't about sweet nothings. It's the male lead systematically dismantling every external threat—scheming relatives, business rivals, past flames—who try to undermine his wife. His loyalty is a brutal, possessive force, and her loyalty is her growing trust in that protection. It's a fortress being built brick by brick.
Another angle is the 'comeback after betrayal' arc, but where the betrayed party never wavers in their inherent loyalty, making the betrayer's regret a thousand times worse. 'Don't Leave Me' by Bai Luwan explores this. The female lead is publicly humiliated and divorced, but instead of breaking, she rebuilds herself with glacial dignity. Her loyalty was to the marriage, and when it's violated, she redirects that fierce loyalty to herself. The ex-husband's desperate attempts to win her back highlight how his disloyalty destroyed the one thing of value he had. The satisfaction is in watching her principled stand, not in his grovel, though the grovel is epic.