Bakumatsu Kourinden Oni

The main character is Yamatomaru, a boy living in the town of Iida. One day, Yamatomaru hears that a child living in the same town has been captured by yokai, and he goes to his rescue by himself. He manages to defeat a few yokai, but is almost defeated by the surviving ones. He is saved from his predicament by Jurota Mibu, a " Kage no Shinsengumi " (Shadow Shinsengumi) whose job it is to exterminate youkai. Jurouta tells Yamatomaru that he has the potential to become a member of the " Kage no Shinsengumi," and so the story begins.