Rin, Archer, Shirô and Saber run into a girl named Illyasviel von Einzbern and her seemingly unstoppable Servant, Berserker, in a long-ranging battle that could destroy the four of them.
Rin finally asks Shirô out on a date, but their enjoyment is cut short when Caster makes her move. Shirô is forced to make a difficult decision to protect the people he cares about.
Rin suspects Kuzuki might be the Master of Caster. With the help of a hesitant Shirô, she implements a dangerous plan in a remote location to test out her theory.