Nanoka is an ordinary girl. While passing through a mysterious portal, she found herself in the Taisho era. There, she gets saved by the exorcist Mao. After that, she came back in the present and realised that she had some strange abilities. Determined to understand them, she returns to the past and becomes involved in Mao’s investigation of brutal murders. She soon came to know about Mao and his sword curse by the cat demon Byoki. Anyone who holds his sword will die. Nanoka takes up his sword when he gets injured.