In the distant future, humanity has terraformed Mars into an oceanic planet to suit their needs. Now known as Aqua, the planet serves as a new home for people discontent with living on Manhome—the planet formerly known as Earth. Being a perfect imitation of Manhome's Venice, the town of Neo-Venezia has inherited all of the rustic charms of the original. Gondolas weave their way through the waterways of the dreamy town while nostalgic alleys await those who travel on foot.

Akari Mizunashi, a young Manhome native, has recently made Neo-Venezia her new home. To pursue her dream of becoming a gondolier tour guide—or Undine—Akari joins the Aria Company, one of the most renowned water guide companies in town. As she basks in a simple lifestyle unavailable on Manhome, Akari cheerily ambles through her daily life in Neo-Venezia: the town where magic and miracles abound.