Kanan Takakiyo is not the ideal student she appears to be. As the popular and athletic chair of the discipline committee at Tama Municipal Votive Academy, she commands respect from the student body, but she is actually a demon from the demon world known as a gourmet demon who has come to the human world to gorge on delicious human souls. Growing bored with demon world cuisine, she transfers to the academy and quickly takes a position that lets her keep students souls free of sin and thus pure enough to eat. She sets her sights on a junior student named Yōji Kyōgi after noticing his soul brims with vitality, and she summons him with the intent of making him her meal. Yōji, however, misinterprets her description of her plan to devour him as an erotic confession and eagerly declares his love. Kanan, who has never experienced romance and panics at his forwardness, accidentally agrees to become his girlfriend.

What follows is a romantic comedy built on a foundation of mutual misunderstanding and Kanan utter inexperience with human emotions and relationships. She has lived for thousands of years but is completely new to love, so every mundane romantic milestone becomes a comedic trial. When Yōji suggests planning a date, Kanan assumes he is talking about sex and awkwardly rejects public locations before demanding they meet at his bedroom, only realizing her mistake after the words leave her mouth. When Yōji asks to hold hands, Kanan believes the act causes pregnancy and ties his hands together to prevent it, which only excites him further. Despite these disasters, she finds herself charmed by his assertiveness and drawn to him, particularly when he buys her croquettes and she experiences the simple joy of sharing food with someone else.

The supernatural elements of the world expand beyond Kanan alone. Her father, Beelzebub, worries about her and sends a succubus maid named Ami to look after her. Ami immediately senses Yōji potent soul and tries to seduce him, but she is both thrilled and surprised when Kanan jealously claims him as her boyfriend and Yōji shows no interest in Ami. Ami begins draining vitality from the student body, which annoys Kanan because she has been working to keep their souls pure, and she enlists Yōji onto the discipline committee to keep an eye on him. Jeanne, a clumsy apostle of God from the heavenly realm, also joins the cast, adding another layer of chaos from the divine side of the cosmic order. Kanan navigates her budding romance alongside the interference of demons and an angel, all while trying to maintain her cover as a human student and keep her relationship on track. The story follows the increasingly close and comedic relationship between Kanan and Yōji as they experience first dates, visits to each other homes, and the awkwardness of young love, with Kanan gradually coming to understand emotions she has never felt before.