The ability of the world to maintain life is fading away. The magical girl Miyu must be sacrificed if the Ainsworth family is to wield the Holy Grail to redeem mankind; but, Miyu's brother Shirou won't give up his sister without a battle. Illya must now intervene and find a method to avert not just Miyu's impending tragedy but also the oncoming catastrophe of the entire globe. But what will Illya do if the only innocent girl whose life must be forfeited in order to save the world?