Fiona is a character who first appears in the first half of the anime, introduced as a young woman living in a remote mountain village within the kingdom of Ikstova. She has black hair worn at neck length and brown eyes. At the time of her introduction, she is twenty years old, making her slightly older than the primary protagonists Allison Whittington and Wil Schultz.

Her background is deeply rooted in the political turmoil of her homeland. Fiona is secretly the twin sister of Francesca, the princess of Ikstova. A decade before the main story, a conspiracy and arson attack on the royal palace resulted in the presumed deaths of the entire royal family, including her parents and her sister. However, Fiona had been hidden away from birth, raised in a secret village by loyalists who protected her from the plot. Following the tragedy, she assumed a simple, quiet life in this remote community, harboring a great secret about her true lineage.

In terms of personality, Fiona is generally portrayed as reserved and proper, fitting a common archetype of a maiden with a quiet strength and an ounce of gumption. While she is not as impulsive or boisterous as Allison, she possesses an inner resolve that becomes evident once her mission is set in motion. Her primary motivation is not personal glory but a sense of duty; she feels compelled to honor her family by reclaiming her rightful place and exposing the conspirators who destroyed her family. To do this, she must impersonate her deceased twin sister, Francesca, and present herself as the long-lost heiress to the throne of Ikstova. A key object in this quest is a pendant that serves as a royal seal, marking its bearer as a member of the Ikstovan royal family and providing the proof she needs to validate her identity.

Fiona plays a significant role in the narrative as a catalyst for one of the major adventures in the first story arc. She first encounters the protagonists Allison and Wil when they are seeking shelter in her village. She reveals her secret to them and requests their help to travel to the capital, Kunst, to interrupt a political speech and declare her identity to the public. Her quest, which involves the assistance of the characters Carr Benedict, Allison, and Wil, ultimately succeeds, allowing her to become the princess of Ikstova.

Her most important relationship develops with Carr Benedict, a dashing and initially flirtatious officer from the Sou Beil Air Force. Over the course of their shared adventure, Benedict’s heroic actions and dedication to her cause lead to a deep mutual affection, contrasting with his earlier, more superficial demeanor. By the second half of the series, which takes place fifteen years later, Benedict and Fiona are happily married. Their relationship is depicted as very loving and affectionate. They have a daughter named Meriel, who, unlike her friend Lillia, is not particularly amused by her parents' frequent public displays of affection for one another.

Fiona undergoes significant development. She transitions from a hidden, anonymous villager living in fear of being discovered into a confident public figure and ruler. In the later timeline, she has fully embraced her role as a member of the royal family and is seen engaged in her royal duties, occasionally being chided by her daughter to focus on state affairs rather than her husband. As a mother, she is part of a close-knit family group, and her home becomes a central location for the next generation of characters. Regarding notable abilities, Fiona does not possess any athletic or combat skills like piloting or marksmanship. Her most significant asset is her secret identity and the royal pendant she carries, which she uses as a tool to claim her political inheritance and change the course of her nation.