The 11th popular series in which Kyosuke Kamizu, a university professor and a famous detective, challenges the mystery of the murder case. A bank clerk Fukushima was killed by a cyanide compound on a crowded train. Newspaper reporter Yamashita and colleague Kaori, who were on board, immediately started interviewing. In addition, Kaori asked Kyosuke Kozu (Masaomi Kondo), a university professor who had previously elucidated the murder of prussic acid by tablets, for cooperation. As a result of the investigation, it is discovered that Fukushima, who was killed, violently attacked a female college student with his colleagues and forced him to commit suicide...

Kyosuke (Masaomi Kondo) and his sister Nobuko (Yoko Moriguchi) were invited to the 10th anniversary party of the travel agency "Pigeon". At that seat, Ayako, the younger sister of President Gentaro, is shot dead. Other venues included Gentaro's brother-in-law, Palau branch manager Kiriyama, secretary manager Anna, and Miyo, who runs a restaurant on Palau Island. A few days later, Nobuko goes on a trip to Palau. She is kidnapped by someone in the field, and Kyosuke and other related parties rush to her. In Palau, there was Toshinosuke, the founder of Pigeon and retired. He was once a detective called "Sakuradamon Demon", but was accused of being arrested 15 years ago and was ousted from the Metropolitan Police Department. It was Kyosuke who proved his innocence.

President Ito, a major apparel maker, was poisoned in the president's office. Kenzo (Baku Ohwada), who happened to be interviewing nearby, rushes to the site. According to his secretary Masae, Ito's ex-wife's younger brother Yoshimoto visited and he started arguing with Ito, but he suddenly escaped. Kenzo asks Kyosuke Kozu (Masaomi Kondo) to investigate. It turns out that Ito's son Takashi, who was killed, is enrolled in Kyosuke Kamizu's university. When Kyosuke Kamizu met at the university, his mother-in-law, Yoko, aimed at his father's fortune and said, "I think he teamed up with designer Kawahara ." Yoko has a relationship with Kawahara, and Ito, who died, was confused because she had an affair with her secretary, Masae. Takashi is said to have already left home and is living on his own.

Based on the comic book by Kenshi Hirokane