Akari Mizunashi, at the age of 15, has left everything behind to travel to Aqua, a sparkling planet covered in water. More than anything, Akari wants to be an "undine" - a female gondolier who navigates the canals of the Aquan city of Neo-Venezia. As she begins her training with the prestigious Aria Company, will she be up to the challenges that await her on the path to achieve her dream?

Akari, Aika and Alice are scheduled for a full day of training with Akira, and what's more, two customers will be along for the ride. They're a couple on their honeymoon; but while the wife loves Undines and riding on gondolas, the husband thinks being an Undine is simple work, and couldn't really care less about the whole thing. It's up to Akira to teach everyone what it means to be an Undine - Undines-in-training included!

It's time to ring in the new year, and everyone in Neo-Venezia has come together to celebrate! Even little Ai has come back from Manhome to take part in the winter festival. But as people gather and memories are shared, President Aria suddenly wanders off. Akari and Ai attempt to track him down, but what they find is a mysterious New Year's gift from Aqua itself.

Two wonderful things have happened: it's time for Neo-Venezia's annual Carnevale, and Ai has come back to Aqua for a visit! As Akari and Ai wander through streets full of bright colors and beautiful masks, they catch a glimpse of Casanova, the mysterious master of ceremonies. Who is the man behind the mask? The two are curious, but they'll need to be careful. You know what they say about curiosity and the cat, after all...