One-hundred and fifty years in the future, terraforming on Mars has caused its polar ice caps to melt, covering 90 percent of the planet's surface with water and making it habitable for humans. Mars is now referred to as Aqua, the water planet. Enter Akari, who leaves Earth for Aqua to become a gondolier, known on Aqua as an undine. In Aria Volume 5, Akrai welcomes the second spring on Aqua. She has the pleasure of accompanying the president of the Aria Company on some errands, and she meets a talented singing undine, one of the elite Three Major Fairies!