Asahi Kuromine, a high schooler who has never once kept a secret, catches his crush Youko Shiragami unfurling a pair of wings in an empty classroom and learns she is a vampire. Youko can stay enrolled only while nobody finds out, so Asahi swears to cover for her. His transparent face makes that hard, and so does newspaper-club president Mikan Akemi, who has known him since childhood. Their classmates turn out to be hiding secrets too, from an alien in a human-sized suit to a werewolf who switches between male and female forms.