The battleship Yamato, the largest and strongest of its time, is on patrol when a lookout spots a massive shape half-submerged in the distance. Believing it to be an enemy submarine, they fire and score a direct hit. But they are shocked when the object emits a strange cry as it sinks beneath the waves. Soon after, something much bigger arrives, the massive kaiju Reigo, seething with rage at the murder of its cub. The monster attacks the Combined Fleet with incredible ferocity and awesome destructive power. The naval forces are caught off guard, and Reigo is able to destroy the escort ships and damage the Yamato before returning to the ocean depths. Now the stage is set for a final battle to unfold between the world's largest battleship and the mysterious dragon-like monster - who will prevail?