Asahi Kuromine, a high-school boy who has trouble keeping a secret from anyone, has a crush on his cool and reserved classmate Yōko Shiragami. While he worries about getting rejected in a similar manner to his confession of love with Class President Nagisa Aizawa, his classmates encourage him to try again. Upon reaching the classroom to confess to Yōko, he finds her unfurling a large pair of wings from her back. Yōko admits to Asahi that she is a vampire, but could only come to school if she hid her true identity from everyone. Asahi swears that he'll be her friend and keep her secret safe…