UFO Robo Grendizer tai Great Mazinger

A newly appointed Vegan general captures Koji Kabuto and learns through interrogation that Great Mazinger is preserved in a museum as a symbol of peace. The invaders steal the dormant machine and turn one of humanity's greatest defenders into a weapon aimed at Earth.

Duke Fleed launches Grendizer against the hijacked Great Mazinger, but destroying it would mean losing an irreplaceable ally. He must withstand its overwhelming attacks long enough to free Koji, recover the machine, and stop the Vegan force behind the assault.