The Holy Grail is a powerful, ancient artifact capable of granting the beholder's every wish. To achieve this power, diverse mages known as "masters" summon legendary Heroic Spirits known as "servants" to fight for them in the Holy Grail War, a catastrophic battle royale. Only the last master-servant duo standing may claim the Grail. Nonetheless, the third war ended in a stalemate, when the Grail inexplicably vanished following the combat. Many years later, the magi clan Yggdmillennia declares ownership of the Holy Grail and plans to depart the Mage's Association. As a result, the Association dispatches 50 top magi to reclaim the Grail, but all but one are assassinated by an unknown servant. The sole survivor is employed as a messenger to deliver Yggdmillennia's message.