Half a year has passed since Shirou Emiya won the Fifth Holy Grail War. In the wake of the conflict, Shirou and his friends are readjusting to peaceful, everyday life. Meanwhile, in a desolate mansion on the outskirts of Fuyuki, a mage awakens: Bazett Fraga McRemitz, Seal Designation Enforcer from the Mage's Association...and former Master in the Holy Grail War.

"Come on, let's continue the Holy Grail War, Bazett Fraga McRemitz. All so we can find your wish this time," a shadow sneers at her. Its name is Avenger, Servant of an eighth class who never existed in the Fifth Holy Grail War. Their unlikely encounter signals that the battle is far from finished.

Shirou Emiya, aspiring champion of justice, steps onto the stage of the Holy Grail War once more. What fate awaits him beyond these four days of destiny?