Kou Yamori is an average middle schooler who struggles to understand the complicated idea of love. Disillusioned with societal expectations, he eventually stops going to school. Battling insomnia due to his lack of direction, Kou starts wandering the quiet streets at night.
One evening, Kou meets a strange girl named Nazuna Nanakusa, who believes people stay awake at night because they're dissatisfied with how they spent their day and can’t find peace until they let go of their inhibitions. Nazuna offers to help Kou with his sleep issues and invites him to her home, where she persuades him to share a futon with her. Although feeling uneasy, Kou pretends to fall asleep—just as Nazuna unexpectedly bites his neck, revealing she’s a vampire!
Kou assumes that the bite will turn him into a vampire, but the process isn’t that simple. To truly transform, he must be bitten by someone he deeply loves. Determined to escape his mundane life, Kou sets a new goal: he’ll fall in love with Nazuna and become a vampire himself.