UFO Robo Grendizer tai Great Mazinger

Great Mazinger is taken over by an alien general at the entrance of a museum, where it's displayed as a symbol of peace alongside Mazinger Z. The alien commander, seeking to exploit Great Mazinger's capabilities, interrogates Koji Kabuto and learns about the robot's existence. As a result, the alien seizes control of Great Mazinger and it becomes a threat to humanity. Duke Fleed, piloting Grendizer, must now stop the robot from being used against its former master.