Battle Unit Zeoth

Battle Unit Zeoth is set in the future, where humanity has been invaded by an ethnic group of alien robots, the Grein. Earth's forces have won the battle and the Grein have fled the solar system. In their retreat, however, the Grein left behind a secret underground base filled with self-replicating Grein machines. Forty-two years after Earth's victory, the Grein base opened and a new attack force destroyed the city of New Age. To retaliate, Earth's military stockpiled a mecha specialized in fighting aliens called the Zeoth. The Zeoth is tasked with stopping the attack force, infiltrating the secret Grein base and destroying the mechanical occupants before a new invading force arrives.