In 2015, the last era when magic still existed. The Humanity Security Agency "Chaldea" suddenly discovered through the near-future observation mirror "Sheba" that humanity was about to be destroyed in the next year of 2016. In order to analyze and interfere with the anomalies and the special codes of time and space, they used the taboo ritual collectively called "Grand Order" to send the magicians back to the past after being transformed into spirits, just to prevent human history from being interrupted. In the distorted Fuyuki Holy Grail War, Saber (Altria Pendragon) turned black and killed all the servants except Caster, and destroyed the entire Fuyuki, and then waited for Caster to come in the Great Hollow. The Caster of this war is Cu Chulainn. He personally said that if the class was Lancer, he could kill Black Saber in seconds. Because of the intervention of the protagonist, Mashu and Olga Marie, this crazy Holy Grail War was successfully stopped, but the disappearance of Saber and Caster meant that no one won the Holy Grail in this war. Leif, who destroyed Olga Marie's soul at the end of the level, and Saber in this war also knew Grand Order. What is going on?