Fifteen year-old Akari leaves 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?
Aika, a budding undine, has a mentor who is quite strict, so she comes up with a solution to get him off her back: she'll run away to the Aria Company!
While training in a particularly tough stretch of water, Akari and Aika meet a girl from Orange planet who seems to be having no trouble at all. Her name is Alice, and she's famous for being one of the youngest yet most talented undines in Neo Venezia.
Akari meets a little girl who gives her a letter and requests she deliver it. But if she is going to have any chance of keeping her promise, she'll have to enlist the help of flying messengers known as Sylphs.
Akari receives a mysterious hand-written invitation to visit Neverland, but she wonders about the uncertainties that await her as she sets off toward a deserted island.
Alice is in a bad mood because her dorm doesn't allow pets. And to top it off, she's realized her left hand isn't as skilled as her right hand. Now she's determined to discover solutions to each as they're probably connected.
The trainees encounter a couple on their honeymoon who think being an undine is simple work. Now it's up to Akira to teach everyone what it really means to be an undine.
It's cleaning time for the Aria Company, and President Aria wants to help out and lead by example for his company. Soon after, President Aria unveils his crime-fighting alter-ego, Nyan-Nyan-Puu!
Aika wants to become as good as the legendary Great Water Fairy, the greatest undine of all time. But when she's sent to visit the legend at her house, Aika realizes she's nothing like she expected.
Winter has come and as a special treat, Alicia suggests that they visit a hot spring. Akari's never seen one before so she's excited to go and soon the remaining trainees decide to join in as well.
On one bleak winter day Alicia, Aika, and Athena sit around a fire, drink cups of hot cocoa, and reminisce about their younger days. Light is shed on how they all came to be friends.
When Akari sets off to visit the oldest bridge in Neo-Venezia, she senses someone is watching her. Once she arrives, she sees the city is entirely different from how it was before. Now she wonders what strange mysteries the old bridge holds.
It's time to ring in the New Year and everyone in Neo-Venezia has come together to celebrate. But soon Akari and Ai stumble upon a strange New Year's gift from Aqua itself.