A UFO appears over Japan. Both the Science Fortress Laboratory and the Saotome Institute decide to send their robots Great Mazinger and Getter Robo to investigate. There was some rivalry between the parties due to the power of their robots. Since the Great was being repaired from an earlier battle, the Getter found the UFO first. However, the UFO turns out to be semi-sentient and repels the Getter Robo. The UFO released a sentient bio-weapon known as Gilgilgan sent by its creator to conquer Japan. The Great Mazinger fights Gilgilgan but with the monster's ability to eat metal, it is badly beaten. The two labs decide to team up to defeat Gilgilgan, despite the protests of their pilots, as Gilgilgan becomes more powerful. Using Boss Borot as bait, Gilgilgan is moved to a deserted island where no metal is found and no collateral damage to the city can be caused (Boss Borot ended up eaten). The Great and Getter manage to work together and defeat Gilgilgan, but the UFO comes back and allows itself to get eaten for Gilgilgan to assume a more powerful form. The battle becomes much more difficult, but the labs are able to find the weakspots on Gilgilgan and instructs the Great and Getter's pilots to strike at those areas, destroying the monster. The movie ends with the pilots on good terms and promising to be friends.
Foreign editions and releases Edit
- French: Go Nagai Robot Movie Collection (2015 DVD and BD release);
- Italy: Go Nagai Robot Movie Collection (2015 DVD and BD release).