Shiki Granbell is a human boy raised by robots on Granbell, an abandoned amusement-park planet in the Sakura Cosmos, where his late grandfather Ziggy taught him to bend gravity using a power called Ether Gear. His lonely life changes when spacefaring content creator Rebecca Bluegarden and her talking cat Happy arrive looking for footage. Befriending them, Shiki leaves Granbell to see the wider universe and join their search for the fabled cosmic goddess called Mother.