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. The doctor himself has been intimidated and forced to collaborate with Galactor. The doctor finally tells Gel Sadra the equation which increases energy and allows the extremely powerful magnetic fields to be used. The doctor is then ordered to lure the Science Ninja Team into their deep sea base. Jun has overheard this by coincidence and knows now that her friend from childhood, Milly, is still alive and has become a Galactor hostage. Jun keeps these dangerous news away from Ken and the others. She sneaks into the deep sea base in the Marihole, together with the doctor.