In an alternate Edo overrun by giant man-eating insects called Mushi, Jinbei Tsukishima comes to the capital to take the post his injured father can no longer hold at the Insect Magistrate's Office. Every other member of the unit hunts Mushi with a technique of their own; Jinbei arrives with none, carrying only a vow to protect every last person in Edo. His first day on the job puts that vow in front of an insect far past anything his training covered.