The Yamanami submarine collides with an American nuclear submarine and crashes into the waters off Japan. Shocked by the news of the crew's death, Hiroshi Fukamachi, commander of the diesel submarine Tatsunami, investigates.

The Seabat, a state-of-the-art nuclear submarine hijacked by Kaieda, surfaces in front of the US Seventh Fleet, which has gathered to sink the Seabat.

The Tatsunami arrives in the region, where the operation is at a standstill after Kaieda's declaration. Fukamachi boards the Seabat to try and stop Kaieda, and learns of Kaieda's true intentions.

Kaieda finally begins to combat the US forces. Wataru Unabara heads to a summit meeting with US President Bennett.

A summit is held between Japan and the US, but neither country recognises the other's claims. Prime Minister Takegami continues negotiations in the hope of avoiding war.

After fighting the US Third Fleet, Kaieda arrives in Tokyo Bay to forge an alliance with Japan. The Japanese government announces a series of important events to the public.