Awakening in a parallel iteration of Fuyuki City, Illyasviel von Einzbern, commonly known as Illya, is disoriented and isolated. Her familiar surroundings are now in shambles, marked by a colossal crater at the heart of her hometown and an inexplicable snowfall during the summer months. Lost without her friends or her magical wand Ruby, the young elementary schooler navigates the remnants of her home, only to be unexpectedly ambushed by an amnesiac girl clad in a gym uniform amidst the chilling climate. This enigmatic figure, identified as Tanaka, holds crucial details regarding the whereabouts of Rin Toosaka, Miyu Edelfelt, and the other missing companions of Illya. Pursued by operatives of the formidable Ainsworth family, the overseers of this alternate dimension, the duo embarks on a perilous journey. Their ultimate destination and Illya's quest to restore the disrupted reality to its former state remain shrouded in uncertainty.