大嶽丸 Ōtakemaru is a kijin—an oni so powerful and so violent that he is considered both demon (ki) and god (jin). He lived in the Suzuka Mountains on the border of Ise and Ōmi Provinces during the reign of Emperor Kanmu (781 to 806). Although his legend is not so well-known today, he was once considered among the most fearsome yōkai in Japanese history. Along with Shuten dōji and Tamamo no Mae, he is part of the Nihon san dai yōkai, or Great Three Yōkai of Japan. (Not to be confused with a separate ranking which ranks oni, tengu, and kappa as Nihon san dai yōkai; or with Nihon san dai aku yōkai, a similar and more recently popularized ranking which swaps Sutoku Tennō for Ōtakemaru.) Because of the time period and locations in which his story takes place, and the fact that his chief enemy was the shōgun Sakanoue no Tamuramaro, it is thought that Ōtakemaru may be a folkloric interpretation of Aterui, a chieftain of the Emishi people of northeastern Japan who waged a devastating campaign against the Yamato Japanese. His legend also serves as the basis of Aomori Prefecture’s famous Nebuta Matsuri, in which large floats depicting warriors defeating oni are parading through the streets. Read more here: http://yokai.com/ootakemaru/