The story is set in mid-18th century Edo, a sprawling metropolis where rational thought clashes with the bizarre and supernatural. The central figure is Hiraga Gennai, an easy-going herbalist and man of science who cannot resist plunging his neck into mysterious incidents. His unlikely partner is Sugita Genpaku, a mad Dutch doctor with a twisted passion for dissection. Together, this mismatched pair investigates a string of strange and macabre events.

The opening case begins with a gruesome discovery: a bound corpse buried in a bamboo grove, its body completely drained of blood. The trail leads Gennai to a playwright named Keian, whose wife recently wasted away from a strange illness. Keian has since fallen for Otami, an attractive musician whom everyone believes to be a demon surviving on blood. The playwright’s manservant, Inumaru, is spotted burying a body, seemingly confirming the supernatural fears. Gennai, however, approaches the mystery as a man of science. He discovers that Otami is not a demon but a victim, her body being eaten away by insects. Inumaru was not serving a demon but committing murders and draining victims’ blood in a desperate, twisted attempt to save her. The case concludes with Inumaru cut down by a policeman and Otami spending her final days in peace with her lover.

Following this, the pair encounter further strange events. In "Cursed Dog," a dispute over a kimono business inheritance involves a supposed curse spread by rabid wolf bites. In "Noh Mask Killer," a series of murders leaves bodies adorned with theatrical masks, leading Gennai and Genpaku to uncover a killing spree motivated by vengeance for an officially ordered slaughter years prior.

The series is written by novelist and screenwriter Amasawa Akira and illustrated by Kanou Seisaku, a pioneer of digital manga creation. It began serialization in the historical manga magazine Comic Ran Twins in 2022.