She was born as Sakatsuki Miyu, the child of God from a parallel world, serving a similar tole to Illyasviel von Einzbern's original role as the Holy Grail. After the fourth Holy Grail War in that world, she was discovered by Emiya Shirou and was adopted by Emiya Kiritsugu to use as a tool, becoming Shirou's adoptive sister. A decade later after the fifth Holy Grail War, she was sent to Illya's world via Shirou's wish on the Holy Grail along with the class cards. Luviagelita Edelfelt adopts her as her younger sister due to her ongoing rivalry with Tohsaka Rin.
