The fabled Yamato battsleship sank to the bottom of the ocean on April 7, 1945. In this fictoinal account the battleship Yamato encounters what it believes to be an enemy submarine. The battleship attacks the underwater entity and sinks it to bottom of the ocean. That entity turns out to be the offspring of Reigo - a legendary deep-sea monster. Now, the mother Reigo surfaces and takes revenge on the battleship Yamato.