The city was abuzz with the news that a number of peddlers and komuso monks were being killed one after the other on the streets. The peddlers were slashed with a kesa-gake and the komuso were stabbed with a spear-like object, and they were killed by the same method. A paper crane with a checkered pattern was always left on the corpse of the konmuso, which made the case seem even more plausible. One day, a ronin named Sakuma Shigezaemon was found slain in the same manner as a series of peddler murders. Okkabiki Dobu sets out to uncover the truth, using Sakuma's Kai koban from the Warring States period as a clue.