Aria is a thirteen-year-old girl who appears in the story as a captive of the Martian army, forced to serve as a substitute for the goddess Athena. Her true nature is that of a child born from the light of Athena's cosmos, created during a battle between the goddess and the dark god Abzu. Her birthday is December 3rd, and her elemental attribute is Light.

Physically, Aria is depicted as a pale-skinned girl with short turquoise hair and blue eyes, often wearing a simple white dress and a golden collar that holds a dark gem. Having been raised in isolation within a tower under the control of Mars and his ally Ionia, she is initially very shy, timid, and innocent about the outside world. Her eyes often carry a sad expression due to her lack of freedom, and she reacts with wonder and curiosity when she first encounters simple things like a dog or a piece of bread. Despite her manipulation, she possesses a kind and gentle heart, and her desire to protect the world from harm becomes a core part of her identity.

Her primary motivation shifts from mere survival to a determined effort to atone for her role in Mars's plans. She feels guilt for having allowed her light to be used to build the Babel Tower and to power elemental ruins that threatened the Earth. As she travels with the protagonist Koga and his friends, she becomes more courageous and independent, finding the strength to actively oppose Mars.

Aria plays a central role in the first major arc of the story. Initially presented as a false Athena, she is rescued by Koga when their light cosmo resonate with each other. After her rescue, she guides the Bronze Saints to destroy the elemental ruins that sustain Mars's power, as her unique light cosmos is the only energy capable of deactivating the cores of those ruins. Her existence is the key to both Mars's ambitions and the heroes' resistance.

Her key relationships define much of her journey. She shares a deep, unexplained bond with the protagonist Koga, as both were born from the same event and their light cosmos naturally resonate. She also forms a close sisterly friendship with the female knight Yuna, who teaches her about the world. Perhaps her most poignant relationship is with Eden, the son of Mars. Eden was kind to her during her imprisoned childhood, giving her a blue cross-shaped earring and trying to show her the outside world, but she does not reciprocate his romantic feelings. Her death ultimately serves as the catalyst that drives Eden to betray his father and rebel against Mars.

Aria’s character development is tragic but complete. She begins as a manipulated tool, a puppet used to legitimize Mars’s rule over Sanctuary. Through her interactions with the Bronze Saints, she awakens to her own will and fights for her own beliefs. In her final moments, she fully awakens to the power of Athena, using her light to rescue Koga from darkness. She is mortally wounded by Mars, who extracts her light attribute cosmos and her staff. In her dying act, she uses the last of her power to teleport her friends to the entrance of the Babel Tower, sacrificing herself for their success.

In terms of abilities, Aria possesses a tremendously powerful light cosmos, comparable to that of a god. This power allows her to perform miraculous feats such as regenerating destroyed landscapes and creating plant life in dead areas. She can generate a warm, tranquilizing breeze that calms others and has demonstrated the psychic ability to teleport living beings. Her light is the antithesis of darkness, capable of dispelling shadows and purifying corruption, and it is essential for disabling the elemental nuclei that power the ruins. She carries a unique staff made of light, distinct from Athena's traditional Nike staff, which serves as a focus for her power.