In the story, there was once a Holy Grail War waged by seven Mages and Heroic Spirits in a town called Fuyuki.
Several decades have passed, and the Yggdmillennia family, who took upon the Holy Grail as its symbol, defected from the Mages’ Association and declared their independence.
The anime premiered on Tokyo MX, BS11, Gunma TV, and Tochigi TV on July 1 at 24:00 (effectively 12:00 a.m. on July 2).
With the Holy Grail War system changed, war at an unprecedented scale, with seven versus seven, breaks out.