Kenmochi enlists Kindaichi and Miyuki's help when a threatening letter arrives at the home of the inspector's childhood friend, Shino Tatsumi, who married into the prestigious Tatsumi family. Upon arrival at the village of Kuchinashi, they encounter armor-clad men. According to Saruhiko, a servant of the Tatsumi household, the men are taking part in a festival to appease the spirits of fallen samurai who were beheaded by the Tatsumi family in the past. The threatening letter is addressed from the Headhunting Samurai, someone thought to be holding a grudge against the family. In this village where the Headhunting Samurai roams and heads go flying, Inspector Kenmochi rises to the challenge of uncovering the secrets kept by the old family.
