A new Holy Grail War is unfolding in Snowfield, Nevada, where mages from across the globe summon Servants—heroic spirits drawn from myth and history—to fight for them. However, this conflict appears distinct from previous iterations. The organization orchestrating it seems to have utilized data from the Fuyuki Grail War for their ritual, leading to peculiar occurrences. Unbeknownst to most participants, this emerging conflict is actually a counterfeit Grail War. Another set of seven true Servants exists, summoned to compete in the genuine Holy Grail War. One of these Servants is a powerful Saber-class who saves the life of Ayaka Sajou, his apparent master, following his summoning. With hidden agendas and unpredictable forces at play, the boundary between the fake and true Grail War becomes blurred, transforming Snowfield into a perilous battlefield.