When Rain Bremen was a young boy, he had a best friend called Ten, and they spent all of their time together. This changed, however, when Ten was attacked by a bandit deep in the woods. Wracked with pain and bleeding out slowly, Ten begs Rain to return to their village to get help. Rain scrambles to obey Ten’s request, but by the time he returns to his friend’s side it’s already too late. Ten has disappeared. Over a decade passes, but Ten is never far from Rain’s mind. Rain continues to wonder about his childhood friend, and what might have happened to him. Then, a little after Rain’s twenty-third birthday, Rain’s father asks him to enter the woods to gather herbs. Rain complies, but he wanders from the path and it begins to rain. Caught up in a sudden storm, Rain slips, cracks his head, and falls unconscious. When Rain awakes, he finds himself in a small cottage owned by a mysterious young man called Zero. Zero claims that he found Rain collapsed in the woods and rescued him, but there’s something strange about Zero. Why does he look so much like Ten – and why does he have such sharp teeth?