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.
“アイアンロックス、ミミー星人登場”
第三黒汐丸が「戦艦大和が現れた！」という緊急電話を残して消息を絶った。ウルトラ警備隊は、アマギとフルハシにハイドランジャーでかつて大和が沈んだ海域の調査を開始させた。しかし、大和の残骸はなく、突然現れたヒトデ型の海星盤に捕らえられてしまう。
