Hakuno Kishinami wakes with no memory at the bottom of the Moon Cell, a lunar supercomputer that has run a Holy Grail War for a thousand years until it stagnated and decayed. Bound to the Servant Saber, Hakuno must climb seven floors, each held by a Floor Master who has to be defeated to advance, while losses inside the simulation are paid for in real lives. Hakuno's climb is an original scenario written for the anime, not a retelling of the Fate/EXTRA game.