Five years ago, Shirou Emiya and his now deceased foster father Kritsugu took in a girl with extraordinary powers who had grown up completely isolated from the outside world. Although Shirou knows that he should only treat Miyu as a means of saving humanity, the two feel more and more like real siblings. But before Shirou can fulfil Miyu's first wish of his own, she is kidnapped by the Ainsworth family, who want to sacrifice her. Now Shirou has to make a difficult decision, because the line between righteous and inhumane deeds no longer seems as clear as he thought...