Kou Yamori is an average middle school student struggling with the complex concept of love. Despite this, he stops attending school due to insomnia caused by idleness. One night, Kou meets a bizarre girl named Nazuna Nanakusa who believes that people stay awake at night because they are dissatisfied with their day and cannot rest until they release their inhibitions. She offers to help him with his sleep issues but invites him over to her place where she convinces him to share a futon with her. Kou feels uncomfortable, pretending to doze off while Nazuna bites his neck and reveals herself as a vampire. While she claims the bite will turn him into one, it's not that simple; in order to transform, he must be bitten by someone he loves deeply. Kou decides to embrace his new goal: falling in love with Nazuna and becoming a vampire.
A restless Ko takes a midnight walk and stumbles upon Nazuna, an enigmatic wo...