Private Detective Kiyoshi Mitarai and Miyuki Ogawa arrive in Fukuyama, Hiroshima Prefecture. They are interested in a case which involves discovered bodies. The bodies were found drifting in the Seto Inland Sea, where the currents repeat every 6 hours.
In 1868, a battle between new government forces and shogunate forces are about to take place in Edo. Katsu Kaishu (Hiroshi Tamaki) wants to avoid useless bloodshed and sends a peace envoy to Takamori Saigō, but Katsu Kaishu is unable to get a response from Takamori Saigō. One day, Katsu Kaishu meets high school teacher Mikako (Satomi Ishihara) and her student Masaya who is captivated by the shogunate. Mikako and her student Masaya tells Katsu Kaishu that they are from the future. Katsu Kaishu takes care of Mikako and her student Masaya, while Mikako hopes to go back to the future where she came from.
