Tita Mu Koshigaya, or Tita to her friends, is a young lady who captains the Cha-Cha Maru, a ship whose business is collecting strange species in the sea of clouds of the planet Ietta, probably a gas giant of some type, and selling them to collectors and zoos. Elysse Aldo Mordish, a young lady her own age, is saved by accident from a rogue section of Ietta's own armed troops, commanded by the armored commander Guizel, who has previously executed Elysse's scientist father. As the military pursues Elysse, it becomes clear that she has the key to a secret that might determine the destiny of the planet's independence.