In an alternate history of the Meiji era where humans and magical beings known as "yōnin" live side by side, half-yōnin girls team up to fight wrongdoers.

Spirit Affairs receives a request to investigate a suspicious piece of merchandise. Susukihotaru, Riken, Bonbori, Hozuki, and Ganryu head to the antique shop "Ori's" where the item is. The woman who owns Ori's, Orikata Aya, runs the place with the little spirit Mugi. The group is surprised to find spirit and human happily living together. Meanwhile, the suspicious item turns out to be a blade with an ominous aura.

The events of the military gala have left Ganryu in low spirits.