Ko Yamori, a disillusioned middle school student, gradually stops attending school and begins wandering the streets alone at night, unable to find his place in everyday life. During one of these outings, he meets Nazuna Nanakusa, a free-spirited and unpredictable young vampire who introduces him to a very different nocturnal world. Fascinated by this new way of living, Ko decides that he wants to become a vampire as well. To do so, however, he must first fall in love with Nazuna. Through nighttime walks, encounters with other vampires, and questions about love, loneliness, and freedom, Ko tries to understand what he truly feels.