Ai Aino

Ai is initially skeptical, impatient and unimpressed by the slow pace of Neo-Venezia. Her older sister's constant praise has raised expectations so high that the real city seems dull when she first arrives.

Akari's company changes her perspective without relying on spectacular attractions. Ai learns to enjoy wandering, conversation and small discoveries, gradually adopting some of Akari's sensitivity to everyday pleasures.

She remains more straightforward than Akari, giving their correspondence a useful contrast. Ai can question things Akari takes in stride while still sharing her growing affection for Aqua.

Ai begins as an ordinary visitor from Manhome and has no special abilities. Her importance initially comes from her perspective as someone encountering Neo-Venezia from outside.

She becomes increasingly knowledgeable about Aqua through her correspondence with Akari and repeated visits. The emails effectively allow her to experience events she was not present for while developing an understanding of Undine culture and Neo-Venezian traditions.

Ai later trains as an Undine at Aria Company. As a Pair and subsequently a Single, she develops formal gondola technique under Akari and practices with other members of the new generation.

Ai's role differs substantially between the manga and anime. In the anime she appears from the opening episode, meets Akari during her visit to Aqua and becomes the person to whom Akari sends regular emails. Their messages provide a recurring narrative frame.

In the original manga, Ai appears much later, but her connection to Akari similarly establishes a younger person whose fascination with Aqua has been shaped by Akari's way of seeing it.

After Akari becomes a Prima and Alicia leaves regular Undine work, Ai moves to Aqua and becomes Akari's apprentice at Aria Company. This creates a new mentor-student relationship that mirrors Akari's earlier training under Alicia.

Ai later becomes a Single and practices alongside Azusa B. McLaren and Anya Dostoyevskaya, continuing the cross-company friendship established by Akari, Aika and Alice.

Akari Mizunashi is Ai's closest connection to Aqua. Their friendship begins during Ai's visit and continues through frequent emails. Ai eventually becomes Akari's apprentice at Aria Company.

Alicia Florence is part of Ai's early experience of Aria Company and the mentor whose place in the training cycle Akari eventually assumes.

Aria Pokoteng becomes familiar to Ai through her visits to Aria Company and later through her own life there.

Azusa B. McLaren and Anya Dostoyevskaya become Ai's fellow Singles and joint-practice partners in the next generation of Undines.

Cait Sith becomes part of Ai's understanding of Aqua's mysteries through Akari's experiences, and Ai later has an encounter that suggests the city's feline wonders continue into her generation.