Conan, Ran, Kogoro, Heiji and Kazuka visit an inn deep in the mountains of Nagano. Heiji acquires a photo of a figure carrying a scythe running across the surface of the inn's outdoor bath. Conan and his friends have come to investigate the identity of this figure who resembles a kamaitachi, a supernatural demon. At the inn they meet writers Daigo Nakama and Midori Koyanagi, who have come to gather information on the incident as well. While searching inside a dark storehouse, Heiji, Kogoro and Koyanagi are attacked.