The story involves a mad scientist, Dr. Hell, who discovers lost robotics technology and uses it to create machine monsters with which to rule the world. Dr. Juzo Kabuto discovers this, and escapes capture. Kabuto prepares for the upcoming invasion with two special scientific breakthroughs: photo-atomic energy, and the Super Alloy Z, processed from Japanium (a new element found only in the stratum of Mount Fuji). Unknown to all, Dr. Kabuto creates the giant robot Mazinger Z out of the Japanium alloy. Dr. Hell`s lieutenant Baron Assler blows up Dr. Kabuto`s mountain villa, but not before Kabuto contacts his grandson KOJI KABUTO for help. Koji discovers his grandfather`s secret laboratory, and thus, discovers Mazinger Z as well.