Fyana originated as Proto-One, the first Melkian perfect soldier forged through genetic and biochemical enhancements. These modifications suppressed most emotions while heightening combat instincts, conditioning her to function primarily as a living weapon. Her incomplete modifications meant she never attained the full capabilities of later perfect soldiers. A mission alongside Chirico Cuvie led to her abandonment following the cancellation of the experiments.

She later emerged in Udo City operating under the alias "Phantom Lady." Chirico's act of naming her Fyana marked a turning point, initiating her gradual emergence as an individual capable of genuine emotion, distinct from her origins as a programmed soldier.

Her physiology demands regular doses of the rare energy substance jijirium to sustain her functions. This dependency fueled events like the mission to A'koba where Chirico and allies sought jijirium for her. During this time, the Balarant perfect soldier Niva, harboring resentment against Red Shoulders like Chirico, kidnapped Fyana. Niva manipulated her, turning her against Chirico and complicating rescue efforts due to the imperative to avoid harming her.

Her relationship with Chirico catalyzed her humanity. Key moments include mutual care during hardships, exemplified when Chirico carried the ill Fyana across Sunsa's oxygen-deprived desert using a makeshift carrier constructed from scrap metal. This demonstrated her physical vulnerability and deepening emotional bonds. After the confrontation with Wiseman, she and Chirico planned to enter cryogenic sleep together, seeking a future without warfare.

Her character arc consistently explores the tension between her engineered purpose as a perfect soldier and her evolving human identity, shaped by interpersonal connections and survival challenges.