Hyakki Yakō

Hyakki Yakō, variation: Hyakki Yagyō, (百鬼夜行, "Night Parade of One Hundred Demons") is a concept in Japanese folklore, where a parade composed of a hundred kinds of yōkai march through the streets of Japan at night.

Myths & Legends
The story that originated the Hiakky Yako is: a young nobleman is ordered to close up his house in Kyoto and move immediately to the new Imperial court in Fukuhara. Although while he's gone a trusted servant stays behind to care for the house, when he returns, he finds the house infested with one hundred yōkai lke Oni, Tengu and others. All those demons were using his house to make a good party. The noble then prays to Buddha and, by dawn, the demons scatter overwhelmed by the light of religion.

There are other versions that say that the noble, in reality, encoutered the parade of demons on the way to his house. Then the demons quickly overtook the carriage and forced it off the road. Upon seeing himself in such a complicated situation, the man sit anxiously on the inside thinking about what to do. The demons then scare aways his attendants and free the oxen in order to chase them across the field. Blue and brown demons and ogres smash the roof in with mallets, batter the wheels with poles and sticks, and set it ablaze with golden balls of fire. But, although the demons do a great job destroying the carriage, when the last of it is consumed by the flames and smokes, the nobleman manages to escape with Buddha's help. Tired, he then sits calmly in a meadow his eyes closes, clicking his prayer beads as he chants a sutra. Now safe from the destruction, he prays until dawn, when the demons scatter back into dark places, unable to face the light of day.

Appearance
It is described as an event where thousands of demons and yōkai walk through the streets of Japan as a parade, led by their supreme commander Nurarihyon.

Countermeasures
According to the account in the Shūgaishō (拾芥抄), a medieval Japanese encyclopedia, the only way to be kept safe from the night parade if it were to come by your house is to stay inside on the specific nights associated with the Chinese zodiac or to chant the magic spell: "KA-TA-SHI-HA-YA, E-KA-SE-NI-KU-RI-NI, TA-ME-RU-SA-KE, TE-E-HI, A-SHI-E-HI, WA-RE-SHI-KO-NI-KE-RI" (カタシハヤ, エカセニクリニ, タメルサケ, テエヒ, アシエヒ, ワレシコニケリ)

Origins
Such story of the Hyakki Yako originated in a Shinto Fire Festival myth about the Kumano Mountains. It is said that, once a year, all the Shinto gods are supposed to meet on this mountain. During the medieval era, the story was connected to the Heian period and coopted by the Buddhists as a tale of blame agains the much despised Heike ruler os 1180, Taira Kiyomori, who insulted the Buddhists by moving Japan's capital from Buddhist-held Kyoto to his clan's stronghold on Fukuhara.

The earliest known scrools depicting the demons night parade is Hyakki Yako Zu, hand draw by artist Tosa Mitsunobu (who lived from 1434 to 1525). The legend was then revived by Toriyama Sekien 300 years later when he publised his collection of Hyakki Yako tales in 1776. His tales inspired many artists during centuries 19th and 20th.

Modern Depictions

 * The Hyakki Yakō is the focus of the anime Nurarihyon no Mago where the protagonist, Nura Rikuo, is the leader of a Hyakki Yakō that is described as a yakuza yōkai group created by Nurarihyon.
 * In the anime Shakugan no Shana, the name and somewhat the idea is used by a notorious smuggler group.
 * In the anime Noragami, the name and the idea of a group made of yōkai is used by a Rock Band that the members dresses as yōkai.