Youkai are a widely-varied collection of various supernatural creatures that pop up in Shinto religion. They have a lot in common with The Fair Folk. Some youkai are good, others are evil, and many are different. Some are mischievous, others avoid humans entirely. Shinto is an animist religion, and youkai are often associated with natural features such as forests and mountains. This word is often translated as "demon" in Western translations, but since that term is generally associated with pure evil, that does not adequately describe the creatures in question — they are more like The Fair Folk, spanning the entire moral range between good, mischievous, neutral, and actually evil. The closest true Western equivalent is probably that of the ancient Roman genii or spirits.
Supernatural creatures drawn from Western sources often turn out to seem more like youkai in Japanese works. For instance, vampires. Fun fact The Japanese word for vampire contains the character for oni. In the West you've got Nosferatu — a grotesque, undead monster who burns in sunlight and murders to preserve his hideous unlife. In Japan you've got exceptionally cuteFanservice protagonist Moka Akashiya, who is not undead, harbors no ill-will towards the sun, and drinks tiny amounts of blood that leave her "victim" light-headed at worst, but who has a Superpowered Evil Side who can (and will if you look at her the wrong way) kick your ass thoroughly.
Henge, a subset of youkai, are magical animals with Shapeshifting powers and human intelligence. They often assume human form and get into all kinds of mischief. Kinds of henge include Kitsune, Tanuki, and Nekomata.
Obake is another Japanese word that can indicate some type of monster. Derived from the word for “to change,” it generally covers the subset of youkai that includes shapeshifting animals and Animate Inanimate Objects. Confusingly, however, the word obake can also be used to refer to ghosts, also known as yuurei. See Stringy-Haired Ghost Girl for more information.
Ayakashi is a word which is roughly synonymous with "youkai" in current day usage, though traditionally it referred to a ghost that appears at sea during a shipwreck.
The list presented below is by no means complete. Many types of Youkai are exceedingly rare to find in modern media and so are not included. On the other hand, some have garnered enough examples to warrant their own pages.
Youkai with their own pages:
Nekomata: A seemingly ordinary cat that develops magical nature through long life. It looks like an ordinary house cat, except for the tail, which splits into two at half-length. While much smarter than it used to be, a nekomata remains just as whimsical, which may be dangerous with its newfound powers of illusion and necromancy. It's said a cat will become a nekomata after turning 100 years old, where upon its tail splits, it starts using human speech, some how gains transformation powers, a greater intelligence, and other odd abilities. The name is often used and confused for catgirls. May be a Mega Neko.
The two-tailed demon-beast in Naruto is a two-tailed cat.
Espeon and Meowstic in Pokémon are based off of this legend.
Chen and Orin from the Touhou Project. Orin, though, is a Kasha, a different type of youkai cat.
Found in the Disgaea series (and are used in quick leveling tricks in BOTH the first and second ones). They are more Cat Girls, however. Capable of producing offspring with humans, as Rutile is half nekomata.
Natsuki, the Cat Girl protagonist of Hyper Police is revealed to be a nekomata in a moment of anger (her tail splits in two)
Jubei and his daughter Kokonoe (a Cat Girl version of this) in BlazBlue. Appropriately, the latter does bring people back from the dead, although since magic is commonplace in that world she uses science to keep the mysterious powers theme. IronTager is the result.
The character Hakumen contemptuously calls them both "bakeneko" (monster/ghost cat), which in Japanese mythology is a general term for any cat Youkai. The video games translated this word as "Grimalkin" in an attempt at a Cultural Translation (which failed, since "grimalkin" is about as obscure as "bakeneko" to an American audience). Official subtitles for BlazBlue: Alter Memory use "Goblin Cat" instead (which is more accurate and conveys Hakumen's insulting tone).
One episode of Kamichu! has a cat named Tyler who is leader of a "city of the cats" where all cats can walk upright and speak. Later, he is explicitly revealed to be a nekomata while tag-team wrestling.
Compared to other werecats in the Monster Girl Encyclopedia, the Nekomatas are rather tame and even give up on a man should he refuse her advance. They are still monsters though, and will eventually assault thier prey to take his spirit energy. Unlike in the myth, Nekomata in this series are this way since birth. And since this world is filled with Cute Monster Girls, her forms are inverted, with the human form being the true one.
Alice's Adventures in Wonderland: The Cheshire cat may or may not be 100 or so years old, and he clearly doesn't have two tails, but he's otherwise a surprisingly close Western analogue to the nekomata. This is almost certainly a case of Strange Minds Think Alike, since it's unlikely Lewis Carroll would have heard of the Nekomata.
Tsukumogami: Inanimate objects that come to life after a hundred years. These can range from weapons to clothes to umbrellas. The umbrella version (karakasa) is typically depicted with one eye, a mouth, two arms and one leg. Another popular one is Ittan-momen, a floating strip of cotton cloth with eyes and arms. Strangely, they avoid electrical energy in common folklore from the 1940's and it is said that no modern object could ever become a Tsukumogami.
In Love Hina, there is the Tsukumogami called "Moe", a near life-sized doll/puppet who comes to life about halfway through the series, disappears after spending some time with Keitaro, and reappears in the sequel OVALove Hina Again.
A variation of Tsukumogami, known as "The Animated", are the primary enemies in the Gaia Online MMO: zOMG!. Players can encounter animated Cotton Balls, Garlic Cloves, Purses, and even imperialistic Lawn Gnomes. Other enemies (including other youkai) exist as well.
Several Pokémon appear to be based on Tsukumogami; unusually, some of these are modern objects, and indeed Electric-types. These include Magnemite (magnets), Voltorb (Poké Ball), Gardevoir (possibly anesama ningyou, a style of paper doll), Shedinja (the discarded exoskeleton of a Nincada after it evolves), Nosepass (Moai statue), Baltoy (shakokidogu), Shuppet (Teru Teru Bozu, a Japanese paper doll resembling a ghost), Banette (Voodoo doll), Bronzor (a bronze mirror), Bronzong (a bronze bell), Rotom's forms (refrigerator, lawnmower, oven, fan, washing machine), the Klink line (gears), Darumaka and Darmanitan (Daruma statues), Trubbish and Garbodor (garbage bags), Litwick (candle), Lampent (lantern), Chandelure (chandelier), the Vanillite line (ice cream cones), the Honedge line (swords) and Klefki (keychain). Though one would wonder how a candle or an ice cream cone would last the required hundred years without melting long before them.
One Urusei Yatsura episode features a karakasa having a feud with a sentient raincloud.
There's a one volume manga called Tsukumo Happy Soul that involves Tsukumogami. while some are fairly normal, the main character's Tsukumogami is a pink vibrator she inherited from her mom that can turn into a boy. It is a bit ecchi, but it ran in a shonen magazine so it's more gag ecchi.
The Anthology Bordertown contains the short story "Demon" which has a Tsukumogami in the form of a teapot.
Yura of the Hair in Inuyasha turns out to be a comb that became a youkai after being used to comb the hair of hundreds of corpses.
In the Izuna games, not only are some of the standard Tsukumogami found as enemies, you can actually make your own! The more you use a weapon, the more its "LUV" stat increases. When it hits 100, you can burn in a Tsukumo talisman to turn the weapon itself into a talisman; anything you stick it on will gain that weapon's special abilities. (It only works on weapons, not armour.) Make enough of these and you can get all the best powers in the game on a single claw.
Oni: These are brutish mountain spirits that share some things in common with trolls and Ogres. The word is almost always translated into English as "demons" or "ogres." They are sometimes depicted as good or bad, but are usually morally neutral and interested in their own affairs. They prefer huge bludgeoning weapons (iron clubs called kanabō being the most common) and hide loincloths (Usually tiger-striped). Sometimes blamed for streaks of misfortune. Others work jobs in Fire and Brimstone Hell as big red devils. Know the different kinds!
A few side characters (The Ogre Triad, the winner of the final tournament, etc.), and probably Jin and Shishiwakamaru, of YuYu Hakusho.
Suika Ibuki and Yuugi Hoshiguma from the Touhou Project. Kasen Ibaraki is heavily implied to be one as well.
The benefactors for the heroes of the Onimusha series; worse demons killed them off so they gave their power to humans. The Game Boy AdvanceOnimusha Tactics game gives nod to the different versions by stating that some escaped this fate by getting jobs in the Underworld.
King Enma and his underlings in Dragon Ball Z, mostly bureaucrats working in Hell.
Lum from Urusei Yatsura is a variation — she's an alien, but of a race obviously based on folktale Oni.
The Imagin of Kamen Rider Den-O are basically an updated version of Oni, being proud and highly idiosyncratic monsters caused by time travel that perform mischief while possessing series hero Ryotaro. The Kamen Riders in Kamen Rider Hibiki are all called Oni, but they are humans who transform with magical instruments to fight the Makamou, evil spirits.
One of the Transformation Rays in Keroro Gunsou essentially turns people into Oni, by cheaply slapping on Oni features, arming them with clubs and turning their clothes into hide loincloths. Female victims tend to wind up looking like Lum.
Drahmin and Moloch from Mortal Kombat, though In Name Only (like many other Japanese-named things in Mortal Kombat, by the way)
One set of Magic: The Gathering featured various Oni. They were classified as Demon Spirits and looked vaguely ogre-like, but they were also served by actual Ogres.
Oni are the template for ogre magi in Dungeons & Dragons (in fact, one early Sourcebook referred to them as "Japanese ogres"). In 4th Edition, they decided to just call ogre magi "Oni" and be done with it, though in the 3E Oriental Adventures, Oni are a very wide grouping of demonic monsters that merely includes ogres.
Oni in Pathfinder are evil incorporeal spirits who manifest into material form, using various humanoid races as templates; the traditional ogre mage, of course, is based on ogres. The most powerful Oni are the yai, based on giants.
In Shadowrun, there is a japanese ork metavariant that looks very much like the traditional Oni and is usually referred to as such. This causes them a fair bit of trouble because although they're still metahuman, society expects them to act like the fairy-tale creatures they resemble...
Mion Sonozaki from Higurashi: When They Cry has an Oni tattooed on her back out of family tradition. She, like the other great families (includes the Furudes). also have Oni blood.
The final level of "The Islands" region of LittleBigPlanet is called "The Terrible Oni's Volcano". Appropriately enough, the final boss is an Oni made of Fire Material.
The first Summoner game takes place partially in the empire of Orenia, a fantasy setting based on an amalgamation of China and Japan. Oni appear as random monsters, but are concentrated in the Forest of Lianshan, where they are said to be the cursed spirits of humans who turn bestial over time. Killing them doesn't remove the curse, and their monster forms will reappear after a time.
Oni of various kinds appear in Muramasa The Demon Blade. One of Momohime's bosses is a huge, orange Great Oni, the boss of all the Oni.
Ogremon of Digimon - though initially portrayed as an evil minion, later on it was revealed to have no interest in anything other than fighting Leomon and allies with the protagonists to help achieve that possibility. There's also Fugamon and Hyogamon, but they've never played anything more than bit parts and thus were never similarly characterised.
Appear as enemy assassins in Guild Wars: Factions. They serve the greater demon Kanaxai who dwells in The Deep.
The world of Mooshu from Wizard101 has Oni as corrupting forces that take advantage of when the Emperor is injured. They possess the bodies of powerful warlords. Like demons from other worlds, they look like anthropomorphic Indian elephants◊
Shin Megami Tensei has not only the basic Oni footsoldier, but even several of the more powerful named Oni, such as Ongyo-Ki and his gang.
Ōkami has something called Gozuki-kei (translated Bovine Demon) which is a sort of superclass for both the Oni and the Ushi Oni. The three monsters that belong to this class are the almost identical Blue and Red Oni and the Bull Charger, which is something between a bull and a giant spider.
There are a few Pokémon based on Oni, the Electabuzz family and the Kami trio specifically.
In Legend of the Five Rings, Oni are demons that enter the mortal world either through some poor fool summoning them, or through the Festering Pit of Fu Leng that connects the mortal and demon realms. They have an endless array of forms, some of which resemble the traditional Oni.
Shinra in Enchanted In The Moonlight is an oni (translated in the English-language release as "demon"). He's first seen in the prologue complaining about how oni are villainized in folk tales like that of Momotaro; he's blunt, brash and a little violent, but good-hearted.
Yuki-onna: Literally meaning "snow woman", Yuki-onna appear as beautiful women in snowy, cold, or mountainous regions. Some incarnations sleep with lone travelers to steal valuable body warmth, others will simply make them get lost during their travels to freeze to death, yet others will kill travelers by tricking them into touching them or a baby they hold in their hands. More benevolent Yuki-onna will either lead the victims to safety and then sleep with them (or just lead them to safety), or simply leave them alone; the more wicked ones will lead them astray to begin with, kill them with the methods described above, or use them.
Non-Japanese example: The Velvets from Neil Gaiman's Neverwhere are very clearly related - one offers to guide the protagonists to Islington's hall and steals Richard's heat with a kiss. The Marquis makes her give it back, though.
Franken Fran has that chapter's patient end up living with one. She's the less-hostile variety.
In the Monster Girl Encyclopedia, Yuki-onna use blizzards to lure men to their cabin. She will treat a man with a home-cooked meal and warm reception, then seduce him. Should he reject her, she will use ice breath which causes him a terrible cold, and the freezing man will seek a warm touch from her. Yukiwarashi, a child Yuki-onna, will sometimes visit a human village and play with human kids. Should she have an interest in a boy, the Yukiwarashi will take him as her husband once she becomes Yuki-onna.
SCP-1529 ("King of the Mountain"), implied to be the cause of many (if not all) of the deaths on Mt. Everest, acts a lot like one: it dresses all in white, can freeze with a touch through sight if sees you looking at it through a telescope, and seduces climbers with visions of tropical paradise.
While Yumi of Senran Kagura is a human, she's designed as a Yuki-onna: Icy blue eyes, pale skin, a white and pale blue kimono, and most importantly, ice powers.
Two of them appear in Ushio and Tora, both having fallen in love with humans. The younger becomes a human, the older shows up during the final battle.
A variant of the yuki onna legend (in which the yuki onna melts due to her victim's display of concern) is discussed in Detective Conan as a subtle way to clue Shinichi in on the solution to a murder mystery.
Two mysteries in The Kindaichi Case Files featured legends of an especially murderous version of the yuki onna called the yuki yasha and wearing a Hanya mask (a type of mask in Noh theater); of course, both times, sightings of such spirits turn out to be the murderer pulling a Scooby-Doo Hoax.
Yukinojo in Enchanted In The Moonlight is named as a "yukibito," and is basically a male version of a yuki-onna, complete with a translucent white veil over his hair in his ayakashi form. He has power over ice and snow, and even in his human form his hands are always cold.
Baku: A relatively benign example, being a tapir-like monster that eats bad dreams.
The second Urusei Yatsura movie and the chapter/episode it was loosely adapted from feature a baku.
Nightmare Inspector has a baku for a main character, who helps rid people of their nightmares in return for being allowed to eat said nightmares.
Baku make an appearance in The Sandman: The Dream Hunters.
In Final Fantasy VI, when a character wakes up from Sleep status on his or her own, a small baku comes by to "eat" their dreams away.
The Pokémon Drowzee (and by extension, Hypno), Munna, and Musharna are baku. Munna and Musharna also take cues from cartoon "dream clouds".
YU+ME: dream contains "a giant elephant-ram-boar-bear thing with purple hair" called a baku. It does live in the dream world, and attempts to eat the main characters' party.
Tapir, the wizard from Cocoron, eventually turns out to be a baku who you have to fight in the game's final battle.
In Naruto a Baku appears as Danzou's summoning and looks like a huge, tuskless fierce elephant, able to suck anything in his trunk.
The baku from Hell Teacher Nube instead of being a benign creature that ate nightmares, ate good dreams and left its victims in a state of utter, suicide-inducing despair. It was actually composed of hundreds of tortured souls who moaned and writhed in the vague shape of the tapir.
Baku from Onegai My Melody, a tapir who has been known to eat black notes, which are basically manifested nightmares.
Merry Nightmare from Yumekui Merry has powers revolving around dreams and nightmares, and she has a strong baku motif.
The film Paprika ends with the heroine getting rid of a destructive dream-turned-real this way.
The baku of Legend of the Five Rings are malevolent. They still eat bad dreams, but they eat their victim's memories as well.
Kamaitachi: Weasel-like creatures that attack in trios: the first one knocks down a traveler with a gust of wind, the second cuts the traveler with its sickle-like claws, and the third applies an ointment that stops the bleeding, leaving the victim with bloodless but inexplicably large and painful wounds. They're essentially the personification of the pain felt during a bitterly cold wind.
Naruto: Temari a special technique that involves summoning a kamaitachi. She is the wind user, while the Kamaitachi does the cutting. The only time it was used, the opponent was too dead to notice if the bleeding had stopped.
One of the Geomancer skills in Final Fantasy Tactics is a wind attack called Kamaitachi that can trigger the Paralyze (i.e. Don't Act) Status Ailment.
Among the first enemies Sir Arthur faces in Ghouls 'n Ghosts are kamaitachi, depicted as small floating creatures with scythes that turn into tornados.
Mienshao also resembles one, except without the blades.
In La-Mulana, Kamaitachi first shows up as a Mini-Boss in the Graveyard of the Giants, and reappears in Hell Temple.
The tenth movie of One Piece feature, among the other creatures under Shiki's rule, the Tsujigiri Itachi (killer weasel) and they actually wield small scythes with blades made from a Kenju (sword-tree) leaf.
The kamaitachi show up in Hell Teacher Nube in all their glory: the eldest sibling carried a cudgel to knock people over or inflict severe bruises; the middle sibling's forelegs were shaped like absurdly sharp blades which could literally cut up anything and anyone; the youngest carried a jar filled with a mending balm. Makoto inadvertently took the latter as a pet, and, as the elder ones tried to find it, they brought catastrophe to the town —nearly killing Nube by slicing him in half until Makoto finally released the younger kamaitachi and it healed the teacher with its balm.
Muramasa The Demon Blade features a series of swords, going from 3 Kamaitachi to 5 Kamaitachi. The user spins holding the sword out in a rainbow like arc, and the number indicates the total of clones plus the user that use the move.
In Ōkami, the Kamaitachi (translated as Poltergeist) come in the form of three sickle-wielding weasels that can fight separately or join their weapons together to form a wheel of blades. Instead of just wind they can also use the elements of fire, lightning and ice.
Two sets of Kamaitachi siblings appear in Ushio and Tora. The first help the heroes out (and one even falls for Tora, though he doesn't return it), the second are Psychos For Hire.
Kamaitachi can be summoned by the Ten Thunders faction in Malifaux.
Tsuchinoko: A snake-like creature with a long, wide body. It is mostly harmless to most people, unless awoken from its sleep as its venom can fell a man instantly.
There's a tsuchinoko as a particularly elusive enemy that serves as a Metal Slime in Castlevania: Aria of Sorrow. Not because it drops a lot of money if killed, but because possessing its soul reduces prices at the shop. It appears in a single room, and not every time you enter it, and tends to disappear quickly.
In Touhou canon, specifically Strange and Bright Nature Deity, Marisa adopted a rather cute tsuchinoko as a pet after chasing it out of a fairy's house.
Nurikabe: A monster that takes the form of an animate section of wall. It has the power to turn invisible, and likes to use this power to impede travelers.
Petopeto-san has Nuri-chan, one of Hatoko's classmates. She is humanoid, but made out of concrete. Her little sister is more of a wall-shaped creature with arms and legs.
Rokurokubi and Nukekubi: These two creatures are Humanoid monsters, the Rokurokubi are human by day but have extremely elastic necks during the night, while nukekubi can detach their heads from their necks and float away in search of human flesh.
Rokurokubi and Nukekubi Examples
Hellboy story "Heads" has him accidentally running across a household of Nukekubi. Needless to say, he hits them and pokes fun at them.
The OVA Hellboy Animated: Sword of Storms includes a scene that's an almost word-for-word adaptation of "Heads". In another scene, Hellboy encounters female Rokurokubi.
Rokurokubi are a HUGE part of Hell Teacher Nube, as the Genre Blind Miki insists on trying out techniques for astral projection and, instead, ends up turning herself into a rokurokubi. She's unable to control this state at first, and honestly believes that Nube, as the resident exorcist, will kill her because she's become a youkai, but he simply shows her how to control this new side of herself and the ability to extend her neck (sometimes across town) becomes another aspect of her personality... one that she uses incessantly to play pranks, annoy others, and, in at least one occasion, save the lives of herself and her friends.
The Fighting Fantasy gamebook Sword of the Samurai had the protagonist visit an entire village of nukekubi, though the book mistakenly referred to them as rokorokubi.
In the Punky Brewster episode "The Perils of Punky," Cheri is taken by the Spirit and turned into either a rokorokubi or a nukekubi (you cannot really tell),
Sekibanki of Touhou is officially called a Rokurokubi, but has flying head related abilities closer to a Nukekubi. However, her one spell card that directly references the Rokurokubi gives her flying head a stretchy neck.
Tsuchigumo and Jorogumo: These spiders are monstrous in size (as big or bigger than a man) that can take human form to seduce travelers. Jorogumo uses a lure to attract travelers to feed her offspring, and often has the power to allure men with a song. Others act as a Shapeshifting Lover. Tsuchigumo can also use illusions to keep his webs hidden and make people ill in order to feed on them.
Tsuchigumo and Jorogumo Examples
The Ero-Game Atlach Nacha has a Jorogumo attempting to blend in with human society. She doesn't do very well with men, but meets a very nice girl...
Though it may have been entirely unintentional, the eponymous creature of Stephen King's It has much in common with this particular brand of youkai. Its true form is a gigantic spider, and throughout the story appears in several humanoid shapes, most notably Pennywise the Clown. The balloons are strictly of King's invention, though.
The Kumogashira demons in InuYasha. Also the main villain, Onigumo/Naraku is strictly associated with spiders.
A Tsuchigumo is fought in a web-filled castle room in Muramasa The Demon Blade. He captures Torahime and her soldiers, and is fought alongside his children, who also appear earlier in the dungeon leading to him.
In the Monster Girl Encyclopedia, Jorogumo is a nice and harmless spider girl by day, but turns into a sadistic rapist when alone with her lover by night.
Tsuchigumo is the name of a boss in Sine Mora. Appropriately enough, it's a huge robot spider that fires out web-like Bullet Hell patterns.
Mimi in Super Paper Mario has some characteristics of a Jorogumo: her true form resembles a robotic Giant Spider, but she usually presents herself in less-unnerving disguises.
Raiju or "Thunder Beast" is a lightning in a weasel-like shape: it's usually represented with many tails and/or legs, poisonous claws, and bright yellow and black fur. Can also appear as a dog, a monkey, a tanuki, a fox, or even a ball of fire and lightning.
InuYasha: The Raiju Brothers Hiten and Manten. They're both humanoid (with Hiten being totally human-like while Manten has a monstrous head) and they do care for each other. The anime filler also introduces their little sister Soten.
Shiro Amakusa in Yaiba turns in a giant, six tailed weasel with huge claws for his showdown with the Kid Samurai. However, it doesn't sport any thunder-related ability.
A Raiju in the form of a crazed lightning ball appear in xxxHolic.
Monster Hunter: Rajang. Thunder? Check. Can appear like a ball of Thunder/Fire? Check. Yellow and Black Fur? Super Check. Looks like any of the described of a Raiju? Yes, as a Monkey. Tails? Sadly, only one, but can be cut and make it lose power.
Ōkami features fire, ice, electric, and wind wheels each with a different sensory organ on them, an eye, lips, ear, and nose respectively. The nose is unintuitively called the Earth Nose.
One of Enma Ai's servants in Hell Girl is a Wanyuudou (name's the same). He can turn into a whole cart to serve as Ai's transportation to her targets. His human form is an old man with a pretty sweet hat.
Several of these under different names appear as enemies in the Castlevania series.
Inuyasha is a half dog-youkai. Inuyasha's father, stepmother, and half - brother Sesshoumaru are full dog-youkai. However, the story distinguishes between what Inuyasha's family is and "inugami" when villagers mistake Inuyasha for one and the gang are confused the mistake could have happened. This is because in Japanese lore "inugami" are a very specific type of sorcerer whose power comes from a dog they've killed and imbued on their behalf.
The series also has a tribe of wolf youkai under the leadership of Kouga. The youkai have power over wolves and are wolves themselves that can transform to human form.
Inugami-gyoubu Tamazuki in Nurarihyon No Mago often appears as a human with of habit of panting with his tongue hanging out. His real form is that of a giant dog.
Inugami play a background role in Muramasa The Demon Blade. Kongiku and Yuzuruha are kitsune, with Yuzuruha trying to stop the release of the singular Inugami sealed in the Kuzuryu blade. as a Historical Villain Upgrade from his established love of dogs, Tokugawa Tsunayoshi is corrupted and eventually highjacked by Inugami.
Inugami (manga) is a manga series by Masaya Hokazono about a boy who finds an inugami. His appearances are those of a extinct Japanese wolf, but he can grow spikes from his back to fight
Inugami (film) is a Japanese film about a Akira, a teacher that falls for a Miki, a papermaker. Miki's family is said to be under the curse of the Inugami.
Inukami! is a Japanese light novel series written by Mamizu Arisawa. Instead of the term "inugami" which is mostly associated with malevolent dog spirits, it uses the word "inukami" to describe a type of benevolent dog spirit. Inukami! revolves around Keita Kawahira, a descendant of a Inukami-tamer clan and a inukami named Yōko, who later is revealed to be actually a kitsune.
Sadaharu from Gintama is implied to be one. Considering that he's a bull-sized white chihuahua with the strength of a bear and his former owners were a couple of miko this is plausible.
Yuzuriha Nekoi (surname is deliberately misleading) in X has a dog spirit Inuki protecting her.
Kuchiha from Amatsuki is possessed by a wolf-like inugami, rumoured to be the last of her kind.
Inugami appear in Shin Megami Tensei games. Sometimes they can even grow into Makami, their more powerful counterparts.
Oinu of the Dancing Blade: Katte ni Momotenshi! series is a dog-youkai in the form of a young human girl. The only dog-like physical feature she has are her ears, which are hidden in her hair and only seldom pop up. She's a benevolent, meek and loyal girl who loves dog-related items, and in Tears of Eden, the power-amplifying artefact she gets is a dog collar which belonged to a legendary and almighty demon dog. The intro movie of the same game also hints that she has a giant, grey-coated dog true form.
Ushi Oni: Or Gyuuki, means Bull Fiend, and is a sort of counterpart to our Minotaur. In some stories it's a demonic looking ox with many tails and claws, in others he's a sort of giant spider, while in others is a sort of wisp fire.
Ushi Oni Examples
The Eight-Tailed Beast in Naruto is a giant bull-like demon with four horns and eight Combat Tentacles in lieu of tails.His name is, ironically enough, Gyuuki
Gyuu Oh from InuYasha is a half-demon called Izumo who turns into a wicked minotaur-like monster after the sunset. As a result he's gone crazy, but unlike the typical stereotype he's a Genius Bruiser.
In Ranma ˝, Pantyhose Taro's monster form can be associated to the Ushi Oni.
A Ushi-Oni like Kaiju appears in Gantz: the upper half of his body is bovine, his lower half is spidery.
Yu-Gi-Oh! has some Ushi Oni-inspired cards. One of them is a demonic bull with a spider body, and the other one is a fiendish minotaur with four tentacles.
Gyuki from Warriors Orochi is one, though he looks more like a boar demon than a bull.
Gyuki from Nurarihyon No Mago is implied to be a Ushi Oni. Heck, his name is the alternate character reading of Ushi Oni.
In Kamen Rider Decade, it's said that, when a Rider - we mean, Oni - in the World of Hibiki chases power obsessively enough to lose his ideals of justice, he becomes an out-of-control Gyuuki. Like what happens to Hibiki himself.
Nuppeppo: A fleshy blob creature that lumbers around in deserted places, mainly temples and graveyards. Has a smell comparable to that of rotting flesh, leading some to believe they are made of corpses. In spite of this, Nuppeppo are generally peaceful creatures.
The Guplin line from Pokémon resemble this creature, being voracious stomachs that emit repulsive gases while digesting their food.
The Mouth Monsters are a trio of brown blobs with large mouths and varying hairstyles. Each of them are seen near blood stains, and are the only NPCs in their respective areas.note Two are found in the Mural World, one in the Storage Room. One of them even has poop on their head, so at least that one doesn't smell good.
Uboa is a rare malicious example, as it traps Madotsuki and takes her to an inescapable world. In the manga, it even assaults her and steals her effects.
Works that feature youkai include:
Adventure Time has the fruit witches in "Dad's Dungeon", which seem to be Futakuchi-onna.
Amatsuki features many various different kinds of youkai, known here as "ayakashi", including spirits, and ghosts. In fact, about half the main cast are ayakashi.
In Azumanga Daioh, during one of the School Festival episodes of, the girls ponder Osaka's idea of an obakeyashiki kisaten ("haunted cafe"), and imagine Chiyo dressed as a nurikabe and Osaka dressed as a karakasa.
Demon's World, a ToaplanArcade Game also known as Horror Story, features many enemies from various mythologies, and in the Japan-esque stage you get to fight kappa, karakasa, rokurokubi, and other youkai.
Hell Girl also features a Hone-onna, or "Bone Woman". A type of vampiric creature which disguises itself as a beautiful mortal woman to lure men away to feed upon their life force.
Harukanaru Toki No Naka De has these creatures among its mook-type villains (somewhat confusingly, they fall under the collective term onryou, "vengeful spirits", which normally refers to ghosts). In the manga/anime adaptations, some of these get more prominent roles, like the last Nue and the Tengu of the Northern Mountains, but otherwise the youkai-like monsters in general are of little importance to the plot.
Hell Teacher Nube. Between these and Obake, it's practically the whole point. If they're not listed among the specific examples above, it's because they're minor characters, but trust us, these (and more) show up.
Inukami!! is almost entirely populated with various animal spirits, Inukami meaning "dog god".
InuYasha, which in addition to the named characters listed includes at least one example of pretty much every other kind of youkai named on this page and a good many more that aren't.
Kamisama Hajimemashita, a manga about a teenage girl who accidentally becomes a Shinto god, naturally features youkai.
Kanokon: Nozomu Ezomori is a 200-year-old wolf spirit, both trying to seduce the protagonist, Kouta Oyamada. In fact, nearly everyone except him are Obake of some sort (sisters, brothers, etc to Chizuru and Nozomu. Many don't show up in the anime, though).
Kanon: Makoto is a kitsune who lost her memory in exchange for the ability to transform. It came with a hefty price.
Karas (which itself is named for the Karasu Tengu) has youkai in a prominent role, and it depicts tensions between the youkai and the humans who have forgotten them.
Karin-dou 4koma: The vast majority of the cast are either magicians or some kind of youkai, generally either tsukumogami (coin, camera, ...) or animal (fox, bird/dog, snake, toad, crow, ...). Somehow, there's a Henshin Hero youkai. In one strip, a few characters discuss the possibility of virtual idols becoming youkai; one dismissing them as too fleeting to take hold and a moment later suggests that god is the original such idol.
Kekkaishi has Madarao, a white dog youkai that has served the Sumimura family since its founding, passed down to them by the founder, Tokimori Hazama. Madarao is able to detect ayakashi with his amazing sense of smell.
Kiki Kai Kai, a series of Cute 'em Up games also known as Pocky & Rocky, includes several kinds of obake as enemies. (Also, the main player character is a miko.)
In the Monster Girl Encyclopedia, Youkai are exclusively Cute Monster Girls of the Zipangu region. Unlike other parts of this world, they've peacefully coexisted with humans long before anyone can remember. The youkai aren't part of the Demon Lord army and there is no Knight Templar religion hunting them down - in fact, powerful monsters like nine-tail Inari are revered as gods.
In Neko-de Gomen!, Kuroda makes a serum that turns people into youkai that fits them best for ten hours.
Ninja Sentai Kakuranger: The enemies are ALL Youkai, nearly all of which have adapted in some way to the modern world. For example, there's a Nurikabe covered in graffiti, a Sand Woman dressed like a hooker, a chariot youkai who's now a taxicab and a gluttony spirit dressed like a fast-food jockey.
Nurarihyon No Mago is based on a mafia-like family of Youkai that live in the present era, in an ordinary city, keeping it safe from other families/groups seeking power.
The Obake Karuta, a set of cards with Yokai themes which were used in the Edo Period. An ancestor of the modern Pokémon and Yu-Gi-Oh! card games.
Omamori Himari features several other Youkai in addition to the aforementioned, including a water serpent in a leading role, a Shutendoji and many others in minor parts. Most of the major ones are Cute Monster Girls.
Phoenix Wright: Ace Attorney - Dual Destinies : The second case of the game takes place in a town that maintains an ardent superstition of the youkai and plays a major role in the order of events (particularly a Karasu Tengu creature called "Tenma Taro" and the fabled nine-tailed Kitsune).
Pocky And Rocky: Nearly every enemy encountered is some form of youkai, and several of the partners throughout the series are as well.
Pokémon has a lot of creatures based on youkai. An example is Mawile, who is based on the futakuchi-onna, a woman with a monstrous, voracious mouth growing out of the back of her head and hair that functions like tentacles. Mawile gains a Mega Evolution in Generation VI, which gives it two mouths on the back of its head.
Randy Cunningham: 9th Grade Ninja has really shown its work for a western cartoon when it comes to the actual Japanese mythological elements, right down to the inclusion of youkai. The feathers of the Tengu were used to create the Ninja suit, and in the episode Evil Spirit Week, Howard becomes possessed by a Tengu.
Rosario + Vampire: There is a reason the school is called Youkai Academy.(Though monsters from many other cultures are largely present as well)
Saiyuki, in which three out of the four main characters are at least part youkai, as are most of their opponents. Unfortunately, the majority are generic 'demons' - i.e., pointy-eared humanoids with claws - rather than Japanese folkloric Youkai.
Samurai Sentai Shinkenger: The enemies are called ayakashi and are based on youkai, but following ayakashi's traditional meaning of "shipwreck ghost", most if not all of them have some kind of sea-creature theme along with their mythic one. The earlier Ninja Sentai Kakuranger and GoGo Sentai Boukenger had youkai-based monsters, and in all cases the monsters were claimed to be the true inspiration for youkai.
Sengoku Youko is rife with these, given that the series is set in feudal Japan and one of the main characters feature a Kitsune.
Touhou Project: Almost every known character, apart from the four-and-a-half human protagonists, a couple ghosts, and a handful of goddesses, is some form of youkai. Whether or not fairies are youkai is also subject to interpretation, both in and out-universe.
In Yes! Pretty Cure 5 GoGo! episode 27, "Rin-chan vs. Ōedo Yōkai!", Shibiretta takes the Cures and mascots back to the Edo period, where they encounter noppera-bō, rokurokubi, karakasa, oni and burabura.
While not actually Youkai in the demon-form, EVE Online has a couple of spaceships named after Youkai. Among those are the Kitsune, a small, but very potent ECM-based ship and the Tengu, a fast, medium-sized, powerful (and incredibly sturdy) ship capable of doing Level 5 Missions with no support, while all other ships require a fleet for those. It's also the general favorite among Mission-Runners, due to its high amount of Firepower.
In Axis Powers Hetalia, Japan talks about the legend of youkai but states that they do not exist. However, England does meet and talks to a kappa and an onion-head youkai, though Japan is skeptical.