When the Earth's ecosystem is disrupted due to global warming, a plethora of prehistoric sea monsters wage war on Japan. Led by the powerful Raiga, the monsters ravage the city of Asakusa.

The giant monster Raiga returns, rising in Atami Harbor and attacking the city. A second kaiju, Ohga, soon joins the chaos, and the two monsters clash, destroying large sections of the city. Defense forces launch two new weapons, the giant tank Kamikaze and the drill tank Gokumei, to meet the the monster invasion head on. But as the beasts work their way to Tokyo, will they be enough to stop the monsters from laying waste to the city?

Set in World War II, the film depicts the story of the real-life Japanese battleship, the Yamato, which is confronted in the Pacific Ocean by giant monsters, including the most fearsome of them all, Reigo.