説話（せつわ）
Setsuwa
The short tale collections of Heian and Kamakura Japan, where oni, tengu and foxes first have stories.
A setsuwa is a short tale, told as true, usually with a lesson; the great collections gather hundreds. Nihon Ryōiki, compiled by a monk around 822, is the earliest and already has a fox who marries a man and a child born of the match. Konjaku Monogatarishū, from about 1120, runs to over a thousand tales from India, China and Japan, and its Japanese volumes are the first large store of yokai stories: an oni at a city gate, tengu who possess monks, foxes in disguise, a courtier who meets the night parade. Uji Shūi Monogatari in the thirteenth century retells the best of them.
These collections give the Heian capital its yokai. Later writers mined them for a thousand years, and several of the oldest yokai on this site, the oni and the tengu above all, are best met here.
Related yokai
Oni
鬼（おに）
The horned, red-skinned oni with a club is a late composite. The word first named an invisible spirit of the dead, then hell's wardens, mountain monsters, outsiders — and even the figure who once chased oni away.
Tengu
天狗（てんぐ）
A mountain being associated with flight, impossible voices, disappearances, and more than one familiar face.
Kitsune
狐（きつね）
A 1930 account from Toyooka describes blurred blue or red foxfire moving restlessly from beyond the mountain to somewhere close by.
Kasha
火車（かしゃ）
Kasha began as the Buddhist fire cart that came for sinners at the hour of death. By the late sixteenth century it was a thing in the thunderstorm that stole the dead from funerals, and only from about the late seventeenth century was it said to be a cat.