UFO Robo Grendizer: Confrontation in the Red Setting Sun

Alien invaders take over Great Mazinger who is at the entrance of a museum next to Mazinger Z as symbols of peace. Grendizer fights the evil invaders and Great Mazinger is recovered. When the Vegan empire dispatches a new general to oversee the takeover of Earth, he quickly manages to capture Koji Kabuto and, learning of Great Mazinger through interrogation, quickly commandeers it from a museum where it was kept as a symbol of peace. It is now up to Duke Fleed aboard Grendizer to stop humanity's former defender from becoming its destroyer.

Duke Fleed is a survivor of the Fleed Planet who is escaped to the Earth, onboard a mysterious "spaceship", where is raised by Dr. Umon as his adoptive son, and known as Daisuke Umon. Years after his arrival, he's faced with the threat of King Vega and his army, who want to conquer the Earth. With his friends Koji and Hikaru (and later his younger sister Maria Grace), Duke decides to fight back using his best weapon - the almighty Grendizer.

No synopsis available.

UFOs and aliens from beyond the stars are common themes in media, entertainment, and other forms of science fiction; however, many individuals have sworn they have seen UFOs and have been abducted in real life! Sit back and watch as the makers of Mazinger take you on a journey through the history of UFO lore. Could it be that UFOs are real and that aliens watch us from afar? [from anime-planet]