Ruscilester, a nightmare world where seven vampire sisters slaughter each other for supremacy. The key lies in "The Demon's Formula" — a conceptual weapon that shatters the world's laws by materializing the owner's twisted perceptions into reality. Shion, the weakest youngest sister, encounters a strange girl named Maroma during her mission to seize the formula from the werewolf Count Vezcacino. Maroma claims to be "human," yet she is a chimera possessing elements of both zombies and Frankenstein's monster.

This inexplicable encounter marks the beginning of the end for the nightmare world.