Geological research following a massive earthquake reveals that Japan is in danger of slipping under the ocean due to tectonic plate activity. Initial projections predict the submersion in 50 years’ time. However, Dr. Tadokoro discovers several other phenomena at work that will bring about a more rapid submersion, in less than a single year. Tadokoro is unable to convince the government of his theories, and his equipment is appropriated for other uses.

Tadokoro’s estranged wife, Takamori, is one of the Prime Minister’s top cabinet officials. The Prime Minister himself is killed during an eruption, and Takamori must watch as the interim Prime Minister makes cold, ruthless decisions regarding the welfare of the people. Takamori appeals again to Tadokoro, who proposes a plan to place explosives under the sea and break Japan away from the sinking plate. Takamori supplies the necessary resources to put the plan into effect, racing against time as more and more natural disasters occur around Japan.

A deep sea sub descends to place the ignition fuse to light off the explosions, but the sub is destroyed in a density current and the ignition fuse is lost. Onodera, another sub pilot, offers to pilot an older deep sea sub to salvage the mission. Despite the slim chances the sub will survive the trip, Onodera insists on the opportunity to save his homeland, for the sake of his loved ones. Onodera dives in the sub and recovers the fuse. With the last of the sub’s power, he manages to place the fuse, activating the explosion sequence. The massive explosions rip the plate apart, freeing Japan from certain doom.