A strange blonde girl with a striking resemblance to Gilgamesh joined the Holy Grail War. But the question is, who is she and who summoned her? Now Rin and Shirou and the other servants must face a new opponent that they have never encountered anything like her. But will Gilgamesh have the courage to say the truth?

In the year 2023, Chaldea Security Organization has completed the Fate project and has assigned one of their Security Officers as a Master to a Heroic spirit with the goal of destroying or retrieving the Holy Grails when and wherever they might appear. Stopping whatever threats are summoned in the process from causing any further harm, and preventing the destruction of Humanity.