As the Moon illuminates the dark sky, demons lurked in the lands. They are heartless and void of mercy creatures that feasts only on humans. Humankind, however, stands ignorant against the rising threat of the demon population, but not all of Humankind. Tomioka Mitsuko wakes up in an unfamiliar room with no knowledge of anything that happened to her before. She realizes the last memory she remembers is the massacre of her foster family - the Tomiokas - happening right before her eyes. That memory happened five years ago. Where was she all this time? What happened?