In a world where humans and different magical races coexist, interactions between them bring both benefits and an increase in heinous crimes by the magical beings. To counter the rising darkness and ensure peace for innocent people and virtuous magical beings, a special intelligence agency called Kamizuchi is established to eliminate corrupt individuals from both groups. The story follows a feared operative known as the Demon Slayer Princess and her succubus partner, Elmia, as they team up to solve crimes, engaging in deadly battles to uphold law and order.