When Kiritsugu found Shirou, he wasted no time in transferring Avalon to Shirou to save his life. What if Kirei was lying in wait, and used his opportunity to kill Kiritsugu? What if he then decided to raise Shirou as his own? Years later, Shirou Kotomine must assist his father in the 5th Holy Grail War, all the while harboring intentions of his own.