Airi Arcadia was born into the Old Arcadia Empire’s imperial family, where she faced a difficult childhood both as a girl in a patriarchal system and due to a chronic illness that left her body frail. Unlike most of their relatives, her brother Lux treated her and their mother with kindness, which often led to him being scorned by the rest of the royal family.

Her maternal grandfather, Wade Roadbelt, openly criticized the corruption and misgovernment of the Old Empire, an act that led to his imprisonment and the banishment of his family, including Airi, from the imperial court. Not long after, Airi’s mother was killed in a carriage accident. The shock of this loss worsened Airi’s illness, leaving her bedridden. Though she attempted to push Lux away by refusing his help, he continued to care for her. Two months later, Airi was sent to live with a count on the country’s border.

During the rebellion against the Old Empire, Lux left Airi in the care of a maid to ensure her safety. However, Emperor Diseld Arcadia, her father, learned of the uprising through a traitor and abducted Airi—unconscious at the time, to use her as leverage against Lux. She was ultimately rescued by Fugil Arcadia, the first prince, who was also involved in the rebellion. Following this event, Airi’s memories were altered so she believed she had simply been asleep in bed throughout the rebellion.

The rebellion succeeded with Fugil’s intervention, leading to the fall of the Old Empire and the rise of the New Kingdom of Atismata. Although Airi and Lux were pardoned, they were burdened with a massive debt amounting to one-fifth of the national budget. Lux took on menial jobs to work toward repayment, while Airi was placed in the Royal Officer Academy as a civil official student, both due to her weak health and as a means for the new royal family to keep Lux under control. Within the academy, she assisted by deciphering ancient manuscripts and updating Drag-Ride manuals, helping to reduce the family’s debt and support Lux in mastering his Drag-Ride, Bahamut.

Airi has shoulder-length light gray hair and gray eyes, traits she shares with other members of the Arcadia family. She is usually seen wearing the standard Royal Officer Academy school uniform. Like her brother Lux, she also wears a black collar, a mark imposed on the surviving members of the former imperial family to signify their status as criminals due to their bloodline.

Airi is portrayed as calm and composed, rarely losing her poise even in moments of crisis, such as during an Abyss attack on the academy. She often takes a critical stance toward her brother Lux, pointing out his faults or questioning his choices, yet her actions reflect deep concern for his well-being. While she trusts in Lux’s strength, she worries when he recklessly overexerts himself.

Despite her maturity, Airi also shows a more vulnerable side. She becomes easily embarrassed when others tease her about her close bond with Lux, revealing her sensitivity beneath her outward composure. Her sharp intellect and diligence are also defining traits, demonstrated through her work in deciphering ancient manuscripts and maintaining Drag-Ride manuals at the Royal Officer Academy. These responsibilities highlight her sense of duty, as she strives to contribute despite her frail health.

Overall, Airi balances maturity and intelligence with moments of youthful vulnerability, making her both a supportive figure for Lux and an important character in her own right.

Airi possesses a remarkably high aptitude for Drag-Rides, surpassing that of most students. However, her frail health and limited physical strength prevent her from utilizing them effectively in combat. As a result, she chose to serve as a civil official rather than as a Drag-Knight.

She demonstrates exceptional scholarly ability, particularly in deciphering ancient documents. Her skill in this area is considered on par with professional specialists of the royal capital, making her a valuable resource to the Royal Officer Academy.

In addition to her academic strengths, Airi has shown capability in strategic observation and management. She is able to assess situations during battle and provide tactical adjustments, supporting her allies despite not fighting directly.

Lux Arcadia
As her only surviving sibling following the fall of the Old Arcadia Empire, Airi deeply cares for and trusts Lux, though she rarely expresses these feelings openly. She often acts critical toward him, masking her concern with scolding or teasing, but her devotion to his well-being is evident.

Noct Leaflet
Noct, Airi’s roommate and fellow first-year student, is also her closest friend. The two are frequently seen together, and Airi often relies on Noct to keep an eye on Lux, ensuring he does not engage in anything inappropriate, much to his frustration. Their bond is further complicated when Noct admits to Airi that she has romantic feelings for Lux, prompting Airi to jokingly plan a “scolding” for her brother for unintentionally monopolizing the affections of the women around him.

Nulph
As prime minister of the New Kingdom, Nulph monitors the Arcadia siblings closely after the fall of the Old Empire. Airi is wary of his intentions, suspecting that he views Lux primarily as a tool to safeguard the kingdom. Her concern reflects both her protectiveness of Lux and her awareness of the political pressures placed upon them as remnants of the former imperial family.