Introduction: There are worlds more than our own.This was shown on the day one merged with ours.Himura Ketsueki, an apathetic, unsociable boy with a curiousity for killing.Theresa Cassius, daughter of a noble Demon family, violent and ruthless on the outside, her inner self hidden underneath a facade.The journey begins as the world is turned upside down, a new era starts, and power is given to those who yearn for it....