The Holy Grail War: a violent battle between mages in which seven masters and their summoned servants fight for the Holy Grail, a magical artifact that can grant the victor any wish. Nearly 10 years ago, the final battle of the Fourth Holy Grail War wreaked havoc on Fuyuki City and took over 500 lives, leaving the city devastated. Shirou Emiya, a survivor of this tragedy, aspires to become a hero of justice like his rescuer and adoptive father, Kiritsugu Emiya. Despite only being a student, Shirou is thrown into the Fifth Holy Grail War when he accidentally sees a battle between servants at school and summons his own servant, Saber. When a mysterious shadow begins a murderous spree in Fuyuki City, Shirou aligns himself with Rin Toosaka, a fellow participant in the Holy Grail War, in order to stop the deaths of countless people. However, Shirou's feelings for his close friend Sakura Matou lead him deeper into the dark secrets surrounding the war and the feuding families involved.

Coming from a renowned magus family, Ayaka Sajou is much expected to partake in the Holy Grail War. But ever since her father and sister's demise in the previous battle, she has grown gloomy and unwilling to involve herself in the matters that killed her loved ones. Soon, she finds herself in grave danger at the hands of a knight and ends up summoning her own Servant named Saber. With him by her side, Ayaka ultimately becomes an official participant in the war she initially wanted to avoid so much.

The world is dying, no longer able to support life. The Ainsworth family can use the Holy Grail to save humanity, but the price of salvation is sacrifice of the magical girl Miyu — but Miyu’s brother, Shirou, won’t let them have her without a fight. Now it’s up to Illya to step in and find a solution that will save not only Miyu, but the entire world from impending doom. But when the price for the world's salvation is the life of a single, innocent girl, what will Illya choose? (Source: Sentai Filmworks)

In the midst of the Fifth Holy Grail War, Caster sets her plans into motion, beginning with the capture of Shirou's Servant Saber. With the witch growing ever more powerful, Rin and Archer determine she is a threat that must be dealt with at once. But as the balance of power in the war begins to shift, the Master and Servant find themselves walking separate ways. Meanwhile, despite losing his Servant and stumbling from injuries, Shirou ignores Rin's warning to abandon the battle royale, forcing his way into the fight against Caster. Determined to show his resolve in his will to fight, Shirou's potential to become a protector of the people is put to the test. Amidst the bloodshed and chaos, the motivations of each Master and Servant are slowly revealed as they sacrifice everything in order to arise as the victor and claim the Holy Grail.