Fate/kaleid liner Prisma☆Illya 3rei!!

Illya awakens alone in a parallel Fuyuki where summer has become winter and her familiar city lies ruined. Ruby, Miyu, Rin, and the others are missing, and the only person she finds is Tanaka, a mysterious amnesiac girl who nevertheless seems to know that the Ainsworth family is responsible.

Searching for Miyu pulls Illya into a struggle over this dying world and the Holy Grail. The Ainsworths possess Heroic Spirit cards and overwhelming power, but Illya refuses to accept a future bought by sacrificing her friend. As allies reappear and hidden histories surface, saving Miyu becomes inseparable from deciding whether an entire world can be saved at all.