Yamatomaru is an ordinary boy living in the town of Iida when word reaches him that a local child has been seized by yokai. Without waiting for help, he charges off alone to attempt a rescue. He manages to defeat some of the creatures, but is nearly overwhelmed when the surviving yokai regroup against him. He is saved at the last moment by Jurota Mibu, a member of the secretive Kage no Shinsengumi — a Shadow Shinsengumi whose purpose is the extermination of yokai. Jurota sees potential in Yamatomaru and tells him he has what it takes to join their ranks, setting the story in motion.