Isami Hanaoka, a fifth-grader, comes from the lineage of the Shinsengumi, as do Soushi Yukimi and Toshi Tsukikage, two of her classmates. The trio's interest drives them to investigate Isami's cellar, where they happen upon an odd array of objects left behind by their ancestors. Additionally, they stumble upon a heartfelt note urging them to combat the wicked Kurotengu group.