It will be finished as soon as possible. We're working as fast as we can, sheesh!
Yōkai of GeGeGe Forest in the sixth anime.
Yōkai (妖怪, lit. apparition, demon, spirit, or monster) are a class of supernatural monsters in Japanese folklore. The word yōkai is made up of the kanji for "otherworldly" and "weird". Yōkai range eclectically from the malevolent to the mischievous, or occasionally bring good fortune to those who encounter them. Often they possess animal features (such as the Kappa, which is similar to a turtle, or the Tengu which has wings), other times they can appear mostly human, some look like inanimate objects and others have no discernible shape. Yōkai usually have a spiritual supernatural power, with shapeshifting being one of the most common. Yōkai that have the ability to shapeshift are called obake. 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).
Shapeshifting yōkai (Obake)
A good number of indigenous Japanese animals are thought to have magical qualities. Most of these are henge (変化), shapeshifters, which often imitate humans, mostly women. Some of the better known animal yōkai include the following:
- Tanuki (raccoon dogs)
- Kitsune (foxes)
- Hebi (snakes)
- Mujina (badgers)
- Ōkami (wolves)
- Bake-Neko (cats)
- Tsuchigumo and Jorōgumo (spiders)
- Inugami (dogs)
One of the most well-known aspects of Japanese folklore is the oni, which is a sort of mountain-dwelling ogre, 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 mostly depicted as evil, but can occasionally be the embodiment of an ambivalent natural force. They are, like many obake, associated with the direction northeast.
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. This virtually unlimited classification includes:
- Bake-Zōri (straw sandals)
- Biwa-Bokuboku ( a lute)
- Bura-bura (A paper lantern)
- Karakasa(old umbrellas)
- Kameosa (old sake jars)
- Morinji-no-kama (tea kettles)
- Mokumokuren (paper screens, with eyes)
Ukiyo-e print of yōkai, by Kawanabe Kyosai 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. Other examples of human transformations or humanoid yōkai are:
- Rokuro-Kubi (humans able to elongate their necks during the night)
- Ohaguro-Bettari (a figure, usually female, that turns to reveal a face with only a blackened mouth)
- Futakuchi-Onna (a woman with a voracious extra mouth on the back of her head)
- Dorotabō (the risen corpse of a farmer, who haunts his abused land)
Hanyō (or Half-yōkai) is a supernatural being who is part human and part yōkai. Hanyō are usually the child of a yōkai and a human, though humans can be transformed into hanyōs. Due to their dual nature, hanyō are often subject to prejudice from both human and yōkai societies because of the mutual hatred between both respective species. Some Hanyō characters are:
Some yōkai are extremely specific in their habits, for instance:
- Azuki-Arai (a yōkai who is always found washing azuki beans).
- Akaname (only found in dirty bathrooms and spends its time licking the filth left by the untidy owners).
- Ashiarai Yashiki (A gargantuan foot that appears in rooms and demands the terrified home owner washes it)
- Tofu-Kozō (a small monk who carries a plate with a block of tofu).
Humans: In the sixth anime, Medama-Oyaji explains that only humans that believe in yōkai can see them. When a human wavers between doubt and belief, their ability to see yōkai clearly is limited. Their vision improves depending on how strong they believe.
Yōkai: Though humans can gain the ability to see most yōkai through believing, yōkai are able to make themselves invisible to them. To the human eye, yōkai appear to flicker when appearing and vanishing. However, unless the yōkai has an ability that makes themselves truly invisible, they can be seen by other yōkai while vanished from humans. On the other hand, they can make themselves visible to any human, even if the human claims to not believe in yōkai, especially to humans that are afraid of them. If a human such as a priest/psychic/spiritualist strongly believes that have cleansed and purified an area inhabited by yōkai, they may become incapable of seeing them. If they were unable to see the yōkai in the first place, then they are unable to see them due to their initial lack of belief rather than the strong belief that their area of work has been purified.  Yōkai can also adapt to their surroundings in various ways. A prime example in the series is Kubire-Oni, who adapts to modern society by using his hair to connect to a phone application and attack his targets. Medama-Oyaji explains that as technology advances, the location in which yōkai live can change, too.