Dr. Oki, the brilliant scientist who designed a new type of submarine, is missing. His son, Susumu, suspects an evil plot by an unknown group. He knows everything about his father's submarine, the "Super 99"—its equipment, weapons, functions, and capacity. Susumu believes that finding his father will expose the secret organization, the Helmet Party, and stop their conspiracy. With the help of his friends and the Marine Corps, he embarks on an underwater quest, unaware of how dangerous his endeavor is…