In the Edo period, Ichitarou, the young heir to a large apothecary shop, has always been stuck in his room due to his weak constitution. As unpleasant rumors about his condition surround him, his grandfather prays for a god to send spirits that will protect the sickly boy. These two guardians, Sasuke and Nikichi, will remain by Ichitarou's side for life and safeguard his health.

As years pass, Ichitarou leaves his room more often, wanting to be helpful and ignoring those who insist that he keep resting instead. One day, Ichitarou sneaks outside without his guardians and ends up staying out until nightfall. On his way home, a bloody man suddenly begins chasing him! The quick-witted Ichitarou is able to escape and discovers the brutal murder scene.

The next day, Ichitarou hears about the murder, but there is something odd about the story—the victim had a different mortal wound from what he saw. With the murderer still at large, Ichitarou continues to gather more details about the peculiar case from humans and spirits alike, which might just lead him to unravel the mystery.