Origins[]
A Japanese yōkai which started out as the demonization of a large jellyfish. He is usually depicted as an elderly man wearing the clothes of a Buddhist monk, and is described as the sort of yōkai that always manages to elude one's grasp. The idea of him being the leader of yōkai is the result of Fujisawa Morihiko's Yōkai Picture Story Compilation - Japan Arc.
In the manga, the Nurarihyon are descibed as Youkai that can alter a persons perception of Reality, also having control over dreams and illusions. Nurarihyon, Rikuo's grandfather, was known as a youkai that could literally walk into a persons house undetected, eating food right off their tables. The Nurarihyon are, essentially, very stealthy youkai who use their control over an enemy's senses to defeat or evade them.