Ayakashi are supernatural beings that vary from harmless to life-threatening attackers of humans, but most individuals are unable to perceive them. Exorcist ninjas are recruited to safeguard people from the latter. Matsuri Kazamaki is a member of a renowned clan of exorcist ninjas who consider all ayakashi as dangerous. His childhood friend, Suzu Kanade, is an ayakashi medium and is a magnet for them due to her boundless vitality. One day, they come face to face with the "King of Ayakashi," Shirogane, who desires to consume Suzu. In the process of rescuing her, Matsuri manages to seal Shirogane's powers, but he retaliates by transforming Matsuri into a girl before fleeing. Now stuck in this new body, Matsuri must come to terms with the strange world of combating hostile ayakashi while also navigating his perplexing relationship with Suzu.