Based on the historical figure of Nobutora, the father of the famous Warring States period general Takeda Shingen. Takeda Shingen has proven himself in battle but there’s an even more capable person in his family, his father Nobutora (lit. Samurai Tiger). The son exiles the father and so the old patriarch goes to Suruga to serve the Ashikaga shogun in Kyoto. Decades later, Nobutora, now 80 years old, learns that Shingen is in trouble and the old man returns home to keep the Takeda family alive as a new leader seeks to usurp leadership of the Takeda’s and starts a fight with the great warlord, Oda Nobunaga.
University professor Kenzo Oshima (Hisamatsu Nobumi) is stabbed to death by someone in an alleyway in Tokyo, and Inspector Totsukawa (Takahashi Hideki) and Detective Kamei (Takada Junji) of the Metropolitan Police Department's Investigation Department's Investigative Division 1 arrive on the scene. According to the first finder, the victim died after saying "Totsukawa...". Oshima was famous as the leading authority on mitochondria, but he had never met Totsukawa... Totsukawa is puzzled, but begins to investigate, and discovers that a suspicious man has been caught on a security camera near the crime scene. Seeking a clue, Totsukawa and his colleagues interview associate professor Hayase Yumi (Kurotani Yuka) and the president of a biotechnology company, Koji Nakazono (Nakamura Shunsuke), who was assisting them in their research, to find out what happened. They find out that the man caught on the security camera is none other than their childhood friend, Akaike Shogoro (Matsuo Satoshi).