The world is entirety covered in a dense sea of clouds. Only the rocky peaks of a couple of islands break through the clouds. They're inhabited with all sorts of strange creatures and animals. A small people called the Rockies are living scattered on the peaks. They're hesitant to venture into the cloud world that's surrounding them. Anisette, an adolescent Rockygirl, brazen and aggressive, runs away to a party on a neighbouring rock. She drags her sister Grisouille, a sensitive and timid girl, along with her. But the party will be over very quickly...