In the year 3000, the threat of the Dark Sea People's invasion of the surface world escalates. Dr. Kitano, who built the giant robot Conbailer X—wielding ultra-radio waves in hopes of annihilating the Sea People—suddenly vanishes one day. To find him, his granddaughter Shizuka infiltrates the Sea People's hideout alone, seeking the secrets of Conbailer X to rescue the doctor. But she falls into a trap, becoming isolated and dragged into a hellish pit. What awaits her is a series of developments beyond imagination—leading to a BAD END.