After a generation of peace, the Earth Federation has begun to build new space colonies to house humanity's growing population. But a new force, the aristocratic Crossbone Vanguard, plans to seize the colonies of the newly-constructed Frontier Side for itself. As their home becomes a battlefield, a handful of young civilians struggle to escape the conflict. Armed with the state-of-the-art Gundam F91, Seabook and his friends put up a desperate struggle against the Crossbone menace...