The talented and self-assured onmyouji Yasunari was sent to probe a powerful ruler's sudden shift toward violence and the suspected spiritual forces driving it. His sole clue leads him deep into the mountains, where he encounters a young man named Ushiwakamaru. Yasunari approaches Ushiwakamaru and swiftly concludes that he poses no danger. However, Ushiwakamaru mistakes Yasunari for a tengu and asks him to teach him how to wield a sword! What exactly is Ushiwakamaru hoping to achieve?