Nanoka is transported to the Taisho era through a portal and is saved from a yokai by exorcist Mao. When she returns to the present, she finds she possesses new abilities, which prompt her to seek answers. Her investigation is complicated by Mao's own inquiry into a series of murders in the past. The murders are linked to a curse affecting Mao and his sword, which is said to be wielded by a cat demon named Byoki.
