Aqua is one of the three students learning under Master Eraqus along with Ventus and Terra. She acts somewhat as a leader of their friend group, often playing the role of mediator between the three and takes on a protective and even caretaking demeanor over Ventus and Terra. She later passes the Mark of Mastery exam, making her a Keyblade Master. Aqua follows after Ventus as he pursues Terra after he flees his failed exam. She is so determined to reunite her friends that she goes to great lengths to assure Ventus' safety once his heart is put into a deep sleep, and even sacrifices her own wellbeing to travel into the Realm of Darkness in search of Terra. She wanders this dark dimension for years, combatting both physical enemies as well as her own self doubts and fears.
Aqua is headstrong, a diligent worker, and full of determination. She is shown to be extremely trustworthy and, while she can at times come across as a bit apathetic and even cold, she demonstrates a fondness and loyalty for her friends that rivals even the likes of Sora. Aqua is driven in her journey to become a Keyblade Master, and while she obviously values herself and takes pride in her work, she will always put the needs of her loved ones before any of her own desires. She is rather self-sacraficial in nature, although her quiet and almost sarcastic personality might lead one to assume otherwise; her form of affection is unique, and highly personal.