Meet Aster, a scavenger living on the outskirts of Pan, a small community trying to rebuild after the fall of civilization. Having been found as an orphaned child, she's considered "Un-Pan" by birth—an outsider—but she still considers it home, even if the residents don't always agree...

Pan is challenged by the nearby territory of Fortuna to forfeit part of their crops or face invasion. Their only option beyond those two choices is arbitration by Celestial Mechanics, a sporting event devised to solve political differences without warfare. A ball game. One that can save the region. And Aster turns out to be a pretty good candidate...

Having lost the first of three rounds against Fortuna, the Celestial Mechanics team of Pan has to learn the rules—and how much room there is to break them—very quickly if they wish to have any chance of saving their indentity and livelihood…

The year is 2068. The place, Fontainebleau forest, ancient home of some of France's mightiest monarchs on the outskirts of what was once Paris. The post-apocalyptic society of Pan survives by growing rice and scavenging among the ruins of a destroyed civilization. Their precarious existence comes under threat when the powerful, technologically advanced Federation of Fortuna forces them into a dangerous choice—submit to Fortuna's rule, or try to best them in a barbaric, ritualized game known as Celestial Mechanics. Pan's only hope? A hot-headed outcast they'd rejected for being "un-Pan": a girl named Aster.