A second world lies behind the one that we know, hidden away behind a thin curtain of lies and secrecy. It has been thousands of years since the Age of the Gods, and the modern era has stripped much of the world of its mystique, but magic stills exists, as do Heroes, and the men and the beasts that necessitate their existence.
Magi hoard and jealously protect centuries of thaumaturgical lore, and fell beasts prey upon human society from the darkest corners of the world. Ill-considered gladitorial rituals cast a long, bloody shadow upon unsuspecting cities, and malignant gods fester and grow to consume them.
It has been six years since the fifth and final Heaven's Feel, the War for the Holy Grail. The ritual has been formally disassembled by Lord El-Melloi II, a participant of the Fourth War; who judged the ritual too great a risk of public exposure to allow its continued existence, following the disastrous corruption exposed during the course of the Fifth War.
No Servants survived the conclusion of the final Heaven's Feel, and some time thereafter, Matou Sakura was readopted into the Tohsaka family at the discretion of her elder sister, the last living member of the lineage. Matou Zouken is missing, having fled Fuyuki City, possibly with the intent of independently restoring the ritual.