![large.jpg](https://media.kitsu.app/anime/poster_images/7359/large.jpg)
One of the most powerful onmyouji from Abe no Seimei's era. He was the rival of Abe no Seimei and fought him nearly a thousand years ago. Ashiya Douman has shown interest in Yakou's reincarnation and seems to have connection with Twin Horn Syndicate/Bicornis Fellowship and Kakugyouki. He also fought with Jin Ohtomo which resulted in Jin losing his leg. (Source: Wikipedia)