Yoshika Miyafuji hails from Fuso, born into a family of clinicians possessing an exceptionally strong magical lineage. Her mother and grandmother both retained high magic power past their twenties, an uncommon trait. Her father, Ichiro Miyafuji, was a renowned researcher who designed the Striker Units used by military witches; he died in a laboratory accident during her youth. This loss forged Yoshika's strong aversion to war and military service. Raised in a rural mountain village with limited exposure to the outside world, she initially planned to inherit the family clinic.

Major Mio Sakamoto recruited Yoshika for the 501st Joint Fighter Wing after recognizing her latent potential. Yoshika resisted due to her anti-war stance but agreed upon learning her father might be alive and receiving a letter from him. She enlisted as a Sergeant despite having no prior flight training or combat experience. During her maiden flight, she successfully engaged in combat defending the Fuso fleet.

Serving as the 501st's combat medic, Yoshika wielded potent healing magic, a telekinesis-lineage ability effective against wounds and illnesses. Initially fatigued after healing one person, she improved to treat over ten consecutively. She also forged exceptionally strong defensive shields, capable of multi-layered or gigantic barriers for offense and defense. Her latent magic power ranked among the greatest recorded, capable of amplifying other witches' magic. Her original Striker Unit, modeled after the Mitsubishi A6M Zero, became overwhelmed by her growing power. She later piloted the prototype Shinden unit, designed by her father and based on the Kyushu J7W, mastering it during its maiden flight.

Personality-wise, Yoshika is earnest, energetic, and kind-hearted yet stubbornly independent. She often acted impulsively to help others, disregarding orders or safety protocols. This led to critical incidents, including an unauthorized attempt to communicate with a humanoid Neuroi that resulted in Sakamoto's severe injury and nearly dissolved the 501st. Her actions also exposed corruption involving Air Chief Marshal Maloney's budget diversion. She developed a flat-chested complex and exhibited accidental perverted behavior, frequently touching or staring at other witches' breasts during daily interactions or unconscious moments. She enjoyed cooking Fuso cuisine, particularly natto, and disliked Britannian food.

Following Gallia's liberation, the 501st disbanded. Yoshika returned to Fuso. Though officially in the reserves, she received a dishonorable discharge for repeated violations during her Neuroi communication attempts, though she remained indifferent, prioritizing becoming a doctor. She later discovered this discharge was rescinded after healing Takami in the Brave Witches spin-off. Six months post-discharge, she temporarily regained her powers to intercept a Neuroi attacking Yokosuka Base. Subsequently, she traveled to Helvetia for medical studies but was drawn back into conflict when Neuroi attacked Gallia. During this crisis, her magic fully reactivated through comrades' encouragement transmitted via radio.

In the Road to Berlin campaign, Yoshika struggled with unstable magic until witnessing her comrade Shizuka sustain mortal injuries. Her subsequent emotional agony unleashed unprecedented power, enabling her to heal Shizuka completely. During Berlin's final battle, she drew most Neuroi attention, allowing the 501st to destroy the core and liberate the city. In this battle, she permanently exhausted her magic to save Sakamoto, using a technique called Reppuzan with Sakamoto's sword. Despite this loss, she affirmed her choice to protect others.

Her post-magic life included resuming medical studies in Helvetia while awaiting the 501st's reformation. She maintained friendships across the unit, notably with Lynette Bishop and Perrine Clostermann, and continued supporting military efforts, such as supplying homemade pastries to the Yokosuka Base.