As the world teeters on the brink of collapse, the Ainsworth family holds the key to humanity's survival through the Holy Grail. However, this salvation demands the sacrifice of the magical girl Miyu, fiercely opposed by her brother Shirou. Illya must now intervene, seeking a resolution to rescue Miyu and avert the looming global catastrophe. Yet, when the fate of the world hangs on the balance of one innocent life, what decision will Illya ultimately make?