When Cho-san was a member of the First Investigation Division 19 years ago, he and Takei were assigned to investigate the murder of Daisuke’s mother, Sayuri. At the time, Cho-san entered the Kambe residence to investigate, and Shigemaru, the head of the Kambe family, surfaced as a suspect in the case. However, the investigative task force folded due to pressure from the top brass of the police, and Cho-san was demoted. Now back to the present, after the mysterious death of Imura, the woman who Daisuke brought into the police station, Kato and Cho-san’s suspicions deepen, so they decide to enter the Kambe residence.

After escaping from the cargo ship, Daisuke and Kambe pursue Shigemaru and arrive at the old site of the 3rd Laboratory owned by the Kambe group, which is the source of all the mysteries. Daisuke confronts Kikuko, the head of the family, with his burning questions, but her answers force him to make a crucial decision. The truth behind the tension and conflict between the three generations of the Kambe family becomes clear.