Filia, whose full name is Filiaregis von Grünewald, is a central character who initially appears as a hardworking maid and student at the RosenBerg Knight Academy. Her primary motivation stems from a deep desire to remain close to her older brother, Hyaweh, leading her to take on various jobs at the academy including cleaning, working in the cafeteria, and other duties just to be near him. This devotion manifests as a pronounced brother complex, and she becomes visibly jealous and confrontational whenever Hyaweh shows interest in other girls. She frequently argues with Fel, another student, over Hyaweh’s attention. Her personality is marked by a somewhat possessive and caring nature, and she has a verbal tic of adding “kana” to the end of her sentences. As a student and worker, she is often seen carrying a mop, which she uses as a weapon, though she rarely participates in direct combat situations.

The narrative later reveals that Filia’s true identity is much grander than her humble academy life suggests. She is the sole daughter of Mystel and Prinseah, the protagonists from a previous installment in the series, making her the lost princess of the Kingdom of Windland. Her true name, Filiaregis, is Latin for “princess,” hinting at this royal heritage. In the story, her character route is uniquely positioned as the last one that can be pursued, and it receives special treatment in its ending, leading many to consider her path as the true ending of the game. In terms of abilities, Filia possesses a talent for healing magic and is able to use powerful recovery spells in the latter part of her specific storyline. Throughout the series, and especially in later installments like Love Maximum, she shows little interest in claiming her royal birthright and continues to lead a life largely indistinguishable from a commoner, often ceding her claim to the throne to another character, Priscilla.