When the famous SL "Lady of Childbirth" traveling on the Yamaguchi Line approached Tsuwano, a passenger saw a man crashing into the tracks from the top of the Usui Tunnel. When the conductor rushed to report it, the man was already dead. Shortly after, the witness passenger had disappeared for some reason! Detective Sato (Takuma), who rushes to the scene, learns that the dead man is Odagiri (Odagiri), a taxi driver whom he met earlier.

Magazine journalist Renji Himura is suspicious of the corrupt nature of Japanese politics and has uncovered a number of parliamentary scandals in his quest to clean up the political scene. His feud with his father, Tetsuya Himura, a member of the House of Representatives of the ruling Republican Party of Japan, reinforces Renji's aversion to political power struggles. Tetsuya is a member of the party's largest faction, the Teikankai, along with his ally Yuichi Tanigawa, who was elected in the same year, but becomes increasingly dissatisfied with the methods of faction chairman and former Prime Minister Shiro Oda. In order to regain the prime minister's office, Oda has brought in Kojiro Suzuki, the current prime minister, and is building a puppet government. Then, Renji receives a tip-off from a mysterious person.