In another world, illyasviel von einzbern finds herself disoriented and endangered without her companions miyu edelfelt or rin toosaka by her side. the once bustling city of fuyuki lies in ruins under a blanket of snow, with a massive hole in its center. upon returning home, illya is shocked to find her family's residence destroyed and no familiar sights around. just as she tries to make sense of this new reality, tanaka, a young girl dressed in gym attire and suffering from amnesia, attacks her. despite her distress, the mysterious tanaka offers assistance to illya, and they take refuge in a nearby playground during the snowfall. however, their safety is short-lived as an agent of the ainsworth family ambushes them while hiding from the snowstorm. though the attacker flees quickly, it seems that more danger awaits illya in this familiar yet altered landscape.