Karisviel von Einzbern enters the Holy Grail War convinced of her own perfection and accompanied by her sister Idasviel, a homunculus custom made with endless affection and a twisted understanding of love to best utilize the Heroic Spirit Brynhildr. Their goal is to use the omnipotent wish-granter to regain their family's lost magic and with it eternity. A miracle that'll allow Karisviel to save those dear to her from inevitably being parted from her by their own mortality.