A long time ago, in a future world, humanity had colonized other planets. But one day, an evil force called the "Arbitrator" appeared and started to wipe out human colonies. The only ones who could stop it were pilots with special advanced mechs.
The game follows the story of two main characters, Leo Stenbuck and Nina Kennedy, who join forces to fight against the Arbitrator and its minions. Along the way, they uncover a conspiracy that threatens the entire galaxy.