Waking up in a parallel realm, Illyasviel von Einzbern finds herself alone and troubled, unable to transform and lacking the support of Miyu Edelfelt or Rin Toosaka. The once bustling Fuyuki City lies in snowy ruins, marked by a massive crater at its heart. Deserted and devoid of life, Illya ventures back to her ruined home, devoid of any semblance of her family. Startled by the enigmatic Tanaka, a girl dressed in a gym uniform with no recollection of her past, Illya reluctantly accepts her aid. Seeking refuge in a playground from the relentless snowfall, the two are unexpectedly attacked by a member of the powerful Ainsworth clan. Despite the abrupt retreat of their assailant, ominous events loom on the horizon in this strangely familiar yet foreboding setting.