Miyu Edelfelt, originally Miyu Sakatsuki, originates from a parallel universe where she was crafted as a perfected Holy Grail with inherent wish-granting capabilities. Born into the Sakatsuki lineage—a family revering children under ten as divine entities—she was cloistered away under her mother’s strict supervision, receiving minimal education. Her presence catalyzed the Fifth Holy Grail War in her world, a conflict predicated on her sacrificial role to advance humanity’s evolution. Rescued by Shirou Emiya after Julian Ainsworth’s release of a destructive black shadow, she joined the Emiya household as Shirou’s adoptive sister. Kiritsugu Emiya, Shirou’s father, initially pursued her power for global salvation but regarded her with detached pragmatism, contrasting Shirou’s conflicted efforts to shield her while affirming her humanity. After Kiritsugu’s death, Shirou restricted Miyu to their home, educating her in theoretical subjects. At ten, her wish to become Shirou’s genuine sibling reshaped their dynamic, fostering familial warmth. This bond fractured when Julian abducted her, spurring Shirou’s Holy Grail War victory to catapult her into an alternate world. There, Luvia Edelfelt adopted her, bestowing the Edelfelt name. As a magical girl wielding the Kaleidostick Sapphire, Miyu displayed a composed, analytical demeanor with scholarly aptitude yet socially naive tendencies, approaching obligations with rigid solemnity. Her rivalry with Illyasviel von Einzbern softened into a profound alliance as their shared experiences forged mutual trust. Though outwardly stoic, Miyu gradually revealed vulnerability, prioritizing Illya’s safety above her own and nurturing fierce loyalty. She exhibited subtle childlike quirks, like animal-patterned sleepwear and seeking Shirou’s affection, while maintaining guarded interactions with others. Her rivalry with Chloe von Einzbern, Illya’s clone, highlighted possessive streaks over Illya’s attention. Central to her narrative is her identity as the Holy Grail and her interdimensional ties. Captured later by the Ainsworths for their ambitions, her origins unravel in *Oath Under Snow*, depicting Shirou’s desperate guardianship in her original world and the calamity exiling her. The film clarifies her “Child of God” epithet, linking her wish-granting essence to the Sakatsuki family’s occult rituals. Across media iterations, Miyu’s arc grapples with reconciling her instrumentalized existence with her humanity. Her bond with Shirou embodies sacrificial kinship, while her partnership with Illya underscores reciprocal resilience. Key confrontations—against Bazett Fraga McRemitz and the Ainsworths—demonstrate her tactical mastery of Class Cards (Saber, Rider) and resolve to safeguard her allies.