Boku no Dokuhime wa Kyou mo Kawaii

When demon princess Raffy married Roren, an immortal knight who safeguards humanity, as part of a new peace treaty between humans and demons, she hadn’t quite expected... that he'd fall for her?! Not only that, he's weirdly stubborn enough to keep trying to get closer to her, despite repeatedly dying from the poison she naturally emits. Just how long will his adoration prevail...?

(Source: Yen Press)