A vampire so overpowered the world sends a teenage girl to kill him, except she ends up protecting him instead. The action hits with real weight, the fanservice lands the jokes it's actually trying to tell, and the cast chemistry makes you care about people in a premise you've seen before. By the time you realize this show has no interest in subverting the harem formula, you're already invested in watching these specific people navigate it.
A legendary vampire thought to exist only in myth suddenly manifests in Japan, commanding twelve powerful spirit beasts and leaving destruction in its wake. The world's governments spring into action, dispatching a special agent to find and eliminate this Fourth Primogenitor before catastrophe spreads further. They send Himegari Yukina, a young apprentice shaman armed with history's most potent anti-vampire weapon, to the supernatural hotbed of Itogami City to locate the threat. What Yukina discovers challenges everything: the Fourth Primogenitor is Akatsuki Kojou, an ordinary high school student who seems completely unaware of his own devastating power. As she investigates whether he's truly the monster everyone claims, their forced proximity creates friction and unexpected connection. Yukina must balance her mission to observe and potentially destroy him against growing doubts about his nature. Meanwhile, other supernatural forces circle, each with their own designs on the powerful vampire. Action erupts across the city as Yukina confronts whether duty and truth can coexist.