Dr. Oki, a celebrated scientist known for inventing the revolutionary submarine "Super 99," has disappeared. His son, Susumu, suspects that an unidentified group is behind his father's disappearance and has sinister intentions. Susumu is intimately familiar with every detail of his father's creation, from its equipment and weaponry to its capabilities and strengths. He is convinced that the key to finding his father lies in uncovering the clandestine organization known as "Helmet Party" and foiling their diabolical scheme. With the help of his team and the Marine Corps, Susumu undertakes a dangerous underwater mission, unaware of the risks involved.