UC0123, most of the lives of the human are still living in the space colonies, and the horrendous war remains in the hearts of the egoism. The Frontier 4 colony is being invaded by the unknown militia entitled themselves as the Crossbone Vanguards. The domain government of the colonies, the Earth United Government fought desperately against the invaders, but gradually, Frontier 4 is captured by the Crossbone Vanguards.
Meanwhile, Seabook and his friends were desperately to escape the devastating war, and dramatically discovered the Gundam F91developed by his mother in the new EUG training ship Space Arc in colony Frontier 1. As his sister Rees unlock the key to F91's bio computer, Seabook began his fight for escaping the war. Will peace ever come to the space colonies.....