Tobe! Isami

Isami Hanaoka is just a fifth grader who happens to be a descendant of the Shinsengumi. Together with fellow descendants and classmates Soshi Yukimi and Toshi Tsukikage, she discovers in the basement of her home, strange artifacts left behind by their ancestors as well as a message urging them to "Fight the evil Kurotengu organization."
(Source: Anime News Network)