After Saber's summoning, Rin Tohsaka takes the lead in bringing Shirou Emiya up to speed on his new reality. The episode is heavy on exposition as Rin explains the fundamental mechanics of the war:

Initially resistant to the idea of a lethal war, Shirou decides to participate only after learning that the fourth Grail War was responsible for the devastating fire he survived ten years ago. He vows to win to prevent such a tragedy from happening again.

Episode 2 of Fate/stay night [Unlimited Blade Works ] , titled " The Curtain Rises ," marks a pivotal shift from the initial action to deep world-building and character philosophy. Following Shirou’s near-fatal encounter with Lancer and his accidental summoning of Saber, the episode focuses on establishing the high stakes of the Fifth Holy Grail War. Plot Summary: The Rules of the Game