An experimental city named Seatoland that swims in the ocean, has been built by the ISO. It is attacked by a Galactor monster called Umiba, and faces total destruction. When this message is received, the Science Ninja Team is mobilized, but Dr. Siski, in charge of Seatoland, refuses to collaborate with them. Milly, the doctor's daughter, has been taken hostage by Galactor during the attack.