The almighty Holy Grail, with the promise of fulfilling any desire, sparked three conflicts in the past, each too brutal and ferocious to leave a victor. Despite this, the affluent Einzbern family is convinced that the Fourth Holy Grail War will be different, because they now have a vessel of the Holy Grail in their possession. The Einzberns employ the despised "Magus Killer" Kiritsugu Emiya solely for this reason, with marriage to their only daughter Irisviel as a contractual contract. Kiritsugu is now at the heart of a brutal survival game, pitted against six other players, each equipped with an old familiar and driven by their own set of ambitions and values. The famed mercenary, accompanied by his own familiar, Saber, quickly discovers his greatest opponent in Kirei Kotomine, a priest who seeks salvation from the emptiness within himself in pursuit of Kiritsugu.