Ai Aino is a character who originates from Manhome, the planet formerly known as Earth. She first travels to the water-covered planet of Aqua as a young girl, initially feeling bored and skeptical because her older sister had spoken so highly of the place. Her perspective changes after she meets and befriends Akari Mizunashi, a gondolier in training. Through this friendship, Ai develops a deep appreciation for the slow, beautiful, and wondrous aspects of life in the city of Neo-Venezia. She becomes the primary recipient of Akari’s daily email messages, in which Akari documents her experiences as an apprentice Undine. These email exchanges allow Ai to grow fond of Aqua from afar, and she visits Neo-Venezia periodically with her family. Over time, Ai decides to follow in Akari’s footsteps, moving to Aqua and becoming an apprentice Undine herself, training under Akari as her mentor. She is pragmatic, observant, and kind, with a grounded personality that balances Akari’s dreamy nature. As an apprentice, she learns canal navigation and absorbs the traditions of her profession.