[4] Thirty million years ago,[citation needed] the country of Japan was part of the continent of Asia, and has since split off into its own archipelago.

In the present day, geophysicist Dr. Tadokoro and Onodera Toshio take the submarine Wadatsumi-1 to the Ogasawara Islands, in order to investigate tremors in the seafloor.

The doctor reveals his two-phase plan: D1-investigating seismic activity in the Japan Trench, and D2-an evacuation of the Japanese islands.

Onodera, drunk and agonizing over the public's ignorance of the impending disaster, meets Abe Reiko for the first time since the Tokyo earthquake.

The Japanese Meteorological Agency reveals devastating news; the original two-year timeline for Japan's sinking is inaccurate, shrinking to just 10 months.

Shipping and air transport production are increased, and a full announcement of Japan’s fate is released to the public nationwide.

The United States, China and the Soviet Union agree to accept large numbers of refugees, but evacuation estimates only increase to eight million per month.

Eleven days before Japan is expected to completely sink, Onodera is shown engaged in rescue efforts, while hoping to reunite with Reiko.

The doctor states that he will remain in Japan until the end, and expresses his confidence in the Prime Minister's leadership ability with the Japanese people's uncertain future.

He cut out a great deal of footage, added new sequences directed by Andrew Meyer and starring Lorne Greene as an ambassador at the United Nations, and released it as Tidal Wave in May 1975.

[2] The American version of the film's new cast members also included Rhonda Leigh Hopkins, John Fujioka, Marvin Miller, Susan Sennett, Ralph James, Phil Roth, Cliff Pellow, and Joe Dante.