Japanese folklorists and historians use yōkai as "supernatural or unaccountable phenomena to their informants". In the Edo period, many artists, such as Toriyama Sekien, created yōkai inspired by folklore or their own ideas, and in the present, several yōkai created by them (e.g. Kameosa and Amikiri, see below) are wrongly considered as being of legendary origin.
There are a wide variety of yōkai in Japanese folklore. In general, yōkai is a broad term, and can be used to encompass virtually all monsters and supernatural beings, even including creatures from European folklore on occasion (e.g., the English bugbear is often included in Japanese folklore to the point that some mistakenly believe it originates from said folklore).
Main aticle: Animal form
Many indigenous Japanese animals are thought to have magical qualities. Most of these are henge (変化), which are shapeshifters (o-bake, bake-mono) that often appear in human form, mostly women.
Main article: Oni
One of the most well-known aspects of Japanese folklore is the oni, which has traits of demons and ogres, usually depicted with red, blue, brown or black skin, two horns on its head, a wide mouth filled with fangs, and wearing nothing but a tigerskin loincloth. It often carries an iron kanabo or a giant sword. Oni are depicted as evil.
Main article: Tengu
A goblin from Japanese mythology that has several supernatural powers and skills in martial arts, the tengu were originally extremely dangerous demons and enemies of Buddhism. Over centuries, their behavior changed from spirits of the damned to active defenders of Dharma.
Main article: Tsukumogami
Tsukumogami are an entire class of yōkai and obake, comprising ordinary household items that have come to life on the one-hundredth anniversary of their birthday.
Main article: Human form
There are a large number of yōkai who were originally ordinary human beings, transformed into something horrific and grotesque usually during an extremely emotional state. Women suffering from intense jealousy, for example, were thought to transform into the female oni represented by hannya masks.
Some yōkai are extremely specific in their habits.