Zero and his fellow mechs have just won the first battle of a war they didn't know or care about. The Beetars are their new enemy. They are an oppressive alien race who've subjected all other races to their rule and tricked humanity into doing their bidding for a century.
The mechs don't know that the first battle was to be the easiest. They will face two more Beetar Commanders, the last being a living legend, before they can claim victory over planet Beetar and end tyranny throughout the galaxy.
But the enemy isn't going to bow down for a ragtag group of humans and mechs. They'll stop at nothing to end the uprising, even going so far as to threaten Earth with total annihilation.
Zero and his pals get upgrades and pick up some unlikely allies along the way, but will it be enough to take down the apex species of the galaxy?