Church Calendar Year: 526 In the world, witches not only exist, but that they practice their sorcery. Yet, in the same world, the people did not know of what magic was. In those times, there was a mercenary who was half-beast and half-human. He and his kind, however, are mocked by humans for their existence and called “fallen beasts”. Day after day, he dreams of becoming fully human, and one day, he encounters a beautiful witch who could change his entire fate. “Do you want to go back? To being a human..? Then in that case, I command thee to become mine escort!” The witch introduces herself as “Zero” and reveals that she is currently in search of a magical tome called “The Book of Zero.” This book can potentially teach someone the power to bring the world to ruin. It was stolen from her by someone and should she get it back, she can help him. In order for the mercenary to become fully human with the power of Zero, he would need to meet her requirement of helping her find this magical tome. The problem is though is that he hates witches, and he would have to serve as the guard to one. Regardless, the two set out for the imperial capital searching for “Number thirteen”, a magician who holds the key to finding “the book of zero”, but it is already too late as they have fallen into a trap…?!