One hundred and fifty years after its terraforming, the surface of the planet Aqua - formerly known as Mars - is almost completely submerged by water. The town of Neo Venezia, a replica of the old Earth city of Venice, is a city that lives in harmony with the water, and is a popular destination for tourists. Akari Mizunashi is a young girl who dreams of becoming a fully fledged Undine - a gondolier who ferries tourists around the beautiful city. With help from her friends she progresses with her training, discovering more of the many wonders of Aqua and Neo Venezia along the way.
Life is a fun adventure for sixteen-year-old Nobue Ito, her ‘average' twelve-year-old sister Chika, the mischievous Miu Matsuoka, timid Matsuri Sakuragi and ‘English' Ana Coppola. Together, these five friends assist each other in the most adorable ways possible. Whether they're teaching someone how to swim, helping with summer assignments, preparing a surprise birthday present or shopping for the cutest clothes, these girls always manage to have a good time no matter what the season or occasion.
In a futuristic Japan, the waters have risen and the population has declined; everything is slowly winding down. In this quiet and reflective time, Alpha, a robot, cares for her owner's cafe in his absence. As Alpha lives her serene and peaceful life, interacting with humans and robots alike, the gentle twilight years of humanity are unveiled.