Oni no Ou to Chigire - Chapter 2 Pg 39

The founder of the Yase family was an onmyouji named Hidetou Yase from the early Heian period who impregnated a female demon that gave birth to a half-human, half-demon child named Hidemori. The female demons name was Fuyou. As her name suggested, her unequaled beauty that could be compared to a celestial maiden appeared to human eyes as nothing more than Hidetous powerful, intelligent wife that lived with him in his mansion. No one knew her true form. Since there were no documents remaining about Fuyous relatives, the particulars of her life other than her name and looks were unknown. Inheriting both his mothers good looks and demon blood, Hidemori was able to see things like demons, apparitions, and spirits. He was also able to visit the Intersection of the Six Realms, the world where demons lived between the human world and hell. He could also employ demons as his servants. On the borders between the human world, and the Intersection of the Six Realms were walls that the residents could not pass. There were demons existing in the human world, and beings in the human world that could transform into demons that were small enough to crawl through the thin cracks of the wall, or large enough to cross over the wall as if there was nothing even there. Since Hidemori had the blood of both worlds, it was natural he could come and go through both as he pleased.