A cargo ship has gone missing at sea and the Ultra Guard are sent to investigate this newest disappearance. They report to General Yamaoka (Kenji Sahara) that witnesses saw what looked like the famous WW2 Battleship Yamato rising from the sea. Furuhashi and Amagi set off underwater in the Hydrangers and find some sort of flying saucer shaped like a starfish. Meanwhile, the weapons-laden Yamato-like warship Iron Rocks surfaces once more and engages the Ultra Guard in a massive fire fight. Learning that the alien Yamato clone will self-destruct, Ultraseven flies into action.
