When the Curtain Goes Up

Back in Shirō's home, Rin explains that he had been chosen as a Master for the Holy Grail War, then explains the basics behind it. When Shirō is unable to comprehend the situation, Rin decides to take him to see Kirei Kotomine, a priest who is her legal guardian and also the overseer of the Holy Grail War. When they arrive at Kirei's church and meet up with him, Shirō learns that once someone is chosen to fight as a Master, their responsibilities are unavoidable. He then learns about the Holy Grail and the purpose of the Holy Grail War. Then, Shirō learns that there were four Holy Grail Wars before the current one, with the latest one taking place ten years ago. When he asks what happens if a Master with dark intentions wins the Grail, Kirei replies that there can be no action taken against the victor, and that the only way he could prevent such a Master from winning is to win it himself. He then adds that at the conclusion of the previous Holy Grail War, a Master with dark intentions touched the Grail, resulting in the fire that Shirō survived, a revelation which horrifies Shirō. Kirei then reveals that before the unworthy Master appeared, another Master actually won the Grail and held it, but because the Grail hadn't fully materialized at the time due to this Master refusing to fight, it deemed him unworthy to hold it. As a result of all the information he had just learned, Shirō finally accepts his responsibilities as a Master. Regrouping with Saber outside of the church, Shirō declares that he will be her Master, and they agree to fight in the Holy Grail War together. Later, Archer informs Rin that since Shirō is now a proper Master, they should attack, but she responds that she still has a debt to pay him and instead decides to let him and Saber return home. Moments later, they are confronted by the same silver-haired girl Shirō briefly met earlier, who is revealed to also be a Master, and her Servant, which Rin identifies as belonging to the Berserker class.