There is a World Beautiful-Skin Competition (WBC) to which the 3 billion women of the world aspire. Carrying on the 300-year legacy of the competition are the twin Bihada sisters, Sara and Saki.

In the year 123 of the Universal Century, skirmishes between the Federation government and the rebel group Crossbones Vanguard echo across Earth's space colonies. One of these small battles breaks in the hometown of young Seabook Arno, forcing him and his friends to flee and ensnaring them in the political turmoil that is quickly evolving into an all-out war. Seabook meets Cecily Fairchild, granddaughter of the aristocrat Meitzer Ronah, who seeks to create a new political power called "Cosmo Babylonia." Using the Crossbone Vanguard as its muscle, the Ronah family schemes to restore aristocratic rule and establish an economic system that will benefit the nobility, thus devastating the quality of life for the common people of the Earth Sphere. Seabook is tasked with piloting the Gundam F91, a mobile suit created by his mother, and must choose between protecting the status Federation's status quo or cooperating with Cecily to find a better way of life for all.

The story revolves around five boys who each possess a trait that have negative effects on them. The handsome boys owe a monetary debt to Sakiko Horinomiya, a girl from a rich family. Wanting the money back, she makes them enter the "Motemen Koshien" contest, so they can pay her back using the prize money.

Mio has feelings for her childhood friend Arata, but can't convey her feelings. One day, as they continue their delicate relationship, the two fight over something trivial. After letting tensions settle, Mio goes to make up with him in the pouring rain. While on her way, she gets into a traffic accident. When she regains consciousness, a mysterious and unfamiliar world appears before her eyes.