Inventor Goro Ibuki creates a humanoid robot named Jet Jaguar. It is soon seized by an undersea race of people called the Seatopians. Using Jet Jaguar as a guide, the Seatopians send Megalon as vengeance for the nuclear tests that have devastated their society.
佐々木勝彦
as Inventor Goro Ibuki
林ゆたか
as Hiroshi Jinkawa
Hiroyuki Kawase
as Rokuro 'Roku-chan' Ibuki
森幹太
as Japan Special Defense Forces Chief
富田浩太郎
as Lead Seatopian Agent
大月ウルフ
as Seatopian Agent
Sakyo Mikami
as Truck Driver's Assistant
Fumiyo Ikeda
as Man from Unit 1
Robert Dunham
as Emperor Antonio of Seatopia
Gentaro Nakajima
as Truck Driver
Ralph Jesser
as Antonio's Aide (Radio Operator in White)
Shinji Takagi
as Godzilla
