Kou Yamori appears to be an ordinary middle schooler — good at his studies, friendly with classmates, and always wearing a calm smile. But beneath that facade, he feels empty. One day, he stops pretending, drops out of school, and soon finds himself unable to sleep. With no way to burn off his restless energy during the day, he begins wandering the streets at night. The quiet darkness brings him some relief, yet he knows his insomnia is more than a passing problem. During one of these late-night walks, Kou encounters a strange girl named Nazuna Nanakusa. She quickly diagnoses the real cause of his sleepless nights: despite quitting school, Kou is still holding himself back from true freedom. Until he learns to live in a way that satisfies him, she explains, sleep will remain out of reach. Just as Kou feels a weight lift off his shoulders, Nazuna invites him to her apartment to share her futon. As he lies there pretending to sleep, Nazuna leans over him—then suddenly sinks her fangs into his neck!