This Illya is very different from the Illyasviel von Einzbern shown in Fate/stay night. Unlike her counterpart, she was born to be used directly in the Fourth Holy Grail War, having been gifted with the knowledge necessary to participate from birth. When she was eight months old, her parents, Kiritsugu and Irisviel, decided to completely abandon the ritual and the Einzberns for their future as a family, sealing her magical abilities and memories to prevent her from becoming involved in the conflict and living a peaceful life. Illya was brought to Fuyuki from Einzbern Castle and raised alongside her adopted brother Shirou while their parents were away, so they were left under the care of Sella and Leysritt most of the time. For ten years, Illya lived a normal life without any knowledge of her background or her parents' activities.