Fate / Kaleid Liner Prisma Illya The Movie: Sekka no Chikai

Synopsis:
The world's destruction progresses. The only thing that can stop it is Miyu's sacrifice that is worthy of the Grail. When Ainsworth asks Illya, the one who carries the title of the world's savior, what she will save between the world and Miyu, she chooses the simple and selfish answer of "both."

In a respite from the fighting, they all rest in the house Miyu and Shirō took care of. When they gather in a circle, Shirō tells them about himself and Miyu. She was the Child of God that granted any and all wishes. Shirō took in the girl who had no one else into the household that he had shared with Kiritsugu.

It has been five years since then, and now they have lived peacefully like siblings. But that peaceful everyday life has now been shattered. They will take her back, but before that, Julian makes his appearance, still seeking in Miyu the miracle that he needs.