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.