In a Holy Grail War, Mages (Masters) and their Heroic Spirits (Servants) fight for the control of the Holy Grail—an omnipotent wish-granting device said to fulfill any desire. Years have passed since the end of the Fifth Holy Grail War in Japan. Now, signs portend the emergence of a new Holy Grail in the western American city of Snowfield. Sure enough, Masters and Servants begin to gather... A missing Servant class... Impossible Servant summonings... A nation shrouded in secrecy... And a city created as a battleground. In the face of such irregularities, the Holy Grail War is twisted and driven into the depth of madness. Let the curtain rise on a masquerade of humans and heroes, made to dance upon the stage of a false Holy Grail.
Due to the anomalous battle taking place in the desert between Archer and Lancer, various factions become aware of the commencement of the Holy Grail War. As the situation unfolds into chaos, Faldeus, tirelessly acquiring information and manipulating the press, catches sight of a girl new to Snowfield. This girl is Ayaka Sajyou, who wanders the city aimlessly. A mark resembling a Command Spell is engraved on her body.
Following the uproar at the opera house, Saber and Ayaka are detained by the Snowfield Police Department. Saber answers the police’s questioning candidly, showing no regard for maintaining the secrecy of the Holy Grail War. As Orlando expresses exasperation in dealing with Saber and the fallout he is causing, Orlando is visited by a certain man—Hansa Cervantes, a priest dispatched by the Holy Church as Overseer in this fake Holy Grail War.
Clan Calatin finds itself in dire straits after interference from Assassin's Master, Jester Karture. Hansa intervenes, taking up arms not as the Overseer of the Holy Grail War, but as an Executor hunting Dead Apostles. With the Servants dismissed from the stage, the two men clash in a battle fought without Heroic Spirits.
The sun has risen, closing the curtains on the night of the battle at the police station. Orlando, busy with caring for the aftermath of the battle, is visited by Francesca. He fails to conceal his frustration towards Francesca’s flippant attitude. Suddenly, a single arrow soars past them, aimed at Gilgamesh and Tiné who are positioned at the Crystal Hill. After intercepting the second arrow fired shortly thereafter, Gilgamesh and Tiné proceed toward the canyon where they discover another Archer waiting for them.
Shortly before the battle in the canyon, in a mansion situated in a swamp, a lone mercenary attempted to summon a Servant. His codename is Sigma. He holds no desires for this world, nor any intention of leaving anything behind. Chosen by the fake Holy Grail for this empty shell of a man was a Servant so singularly unique that it could never be summoned in a normal Holy Grail War...
After leaving the detention center, Saber and Ayaka wander through Snowfield in search of allies. Before long, the two entered a forest made home by Lancer, the Servant who recently engaged in a spectacular battle against Archer. Challenged to prove his prowess and determine whether they would make suitable allies, Saber unleashes his Noble Phantasm as Lionheart.
Prior to the battle between Saber and Lancer, Halri Vorzak, a girl who harbors deep hatred for the world of magecraft, summons a Servant of her own. However, what answers her call is an utterly uncontrollable and aberrant Heroic Spirit. As its claws tear through her abdomen, her life begins to trickle away until a lone homunculus reaches out to grasp her dying hand.
