When Kyuta, a young orphan living on the streets of Shibuya, stumbles into a fantastic world of beasts, he₂s taken in by Kumatetsu, a gruff, rough-around-the-edges warrior beast who₂s been searching for the perfect apprentice. Despite their constant bickering, Kyuta and Kumatetsu begin training together and slowly form a bond as surrogate father and son. But the unlikely pair will be put to the ultimate test; a final showdown.