The so called “Night Parade of a Hundred Demons” that appears throughout Japanese mythology, the Hyakki Yagyo is a much more civil organization than is often portrayed in legends, and exists as a sort of governing body for Youkai across the entirety of Japan. Not all creatures of the night and legendary monsters recognize the Hyakki Yagyo’s authority, but enough do to give its leaders real power and political pull everywhere in the country. In return, the group offers assistance in all matters and support to all its members.
Every Summer, for several nights, all members of the Night Parade come together in a great festival that is said to pass through every major street in Japan, a procession of dancing, wheeling, and cackling Youkai. During these festivities, all laws of the organization are lifted, and each Youkai allows itself to act according to its true nature. Because of this, the actual Hyakki Yagyo, when it takes place, is very dangerous to humans, and those who live in areas it passes through know to stay well indoors for the duration of the event.
The leader of the Hyakki Yagyo, a powerful Youkai known as Nurarihyon, decided once to leave and explore the country on his own, and has been missing from the role for many years. In his absence, Hitotsume-nyudo has taken control of the organization, exerting her power through her own powers and those of her many daughters. Her authority is generally recognized, but there can be no Night Parade without Nurarihyon at its head, and so the Youkai of the group continue to grow more restless with each year he is away.