Battle Unit Zeoth

Battle Unit Zeoth is set in the future, in which humanity is invaded by an alien robot race, the Grein. Earth's forces have been victorious in battle and the Grein have fled the solar system. However, in their retreat, 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's mission is to stop the attack force, penetrate the secret Grein base and destroy the mechanical occupants before a new invasion force arrives.