High schooler Hakuno Kishinami is struggling to comprehend his shattered memory, and he comes to school with a throbbing headache. Sitting by the window in his class, he notices two girls battling outside, causing the glass to shatter. However, despite the chaos, the students remain unfazed. Suddenly, a knight in armor arrives with his lance, killing the students and forcing Hakuno to flee for his life.
After managing to escape from the deadly knight, Hakuno realizes that he has completely lost his memory, except for the phrase "Holy Grail War." Trying to find his way, he roams the deserted school, but is suddenly attacked by two strangers. Injured and unsure of his identity, he clings to life.
As the two men are about to finish him off, a woman in a striking red dress appears and calls out to him. Pulling him back from the brink of death, she introduces herself as the Master and offers to help him. Drawing her sword and confronting the attackers, she forms a pact with Hakuno, promising to guide him through the upcoming challenges.
