In the battle against the True Ancestor, the church's saintess "Iris Chromel" has become a vampire. Facing the crisis of being expelled from her position as a saintess due to her transformation into a demon, she hears of a holy relic deep beneath the labyrinth city that can completely seal her vampiric powers. Thus, she sets out for the labyrinth city... Will she be able to conquer the dungeon and return to being human?