Ai is a young girl from Manhome, the planet formerly known as Earth. Her full name is Aino Ai. She first travels to the water-covered planet of Aqua and its city of Neo-Venezia with her parents for a vacation, initially feeling reluctant or unimpressed due to her older sister’s boasting about the city. After meeting Akari Mizunashi, a trainee Undine, she begins to see the unique charm and beauty of Neo-Venezia, transforming her frustration into fascination. This encounter leads to a lasting bond, and Ai becomes Akari’s regular email correspondent, a narrative frame through which Akari shares her daily discoveries. Over time, Ai returns to Aqua for events such as the Carnevale festival, where she encounters mystical beings like Cait Sith, and eventually becomes a resident. She joins the Aria Company as a Pair apprentice Undine and Akari’s direct junior, training alongside peers Azusa and Anya. Ai’s personality evolves from sullen and skeptical to cheerful and open, adopting Akari’s wonder-filled perspective and learning to appreciate the quiet marvels of Neo-Venezia.