Yo-kai are spiritual beings whose influences are responsible for almost every one of the strange and paranormal events in the human world. Most of these influences range from sudden changes in the behavior of people or abnormal weather in otherwise normal days, as well as unexpected landscape changes or control over a different force of nature. Yo-kai tend not to change their behavior whatsoever and stick to their own different personalities.
Yo-kai are in no way related to ghosts (which is more strongly stated in the manga). Yo-kai may have similar attributes to ghosts like if somebody dies and is reborn as a Yo-kai however, this can only happen if they had a strong reason to become one such as Jibanyan who wanted to defeat trucks to prove himself worthy to see Amy again. All Yo-kai are able to eat, sleep and be in the physical realm unlike ghosts and it is even stated that it is very rare for a human to become a Yo-kai in M01. The only known ghost Yo-kai is Shogunyan, though only in the manga.
With some exceptions, most Yo-kai are invisible to humans without the help of an item such as the Yo-kai Watch. In some cases, Yo-kai can join human societies by putting a magical leaf on their heads, as seen by Komasan, Komajiro and Rawry in the anime; through more conventional forms of shape-shifting, such as Kyubi, Mimikin and Robonyan; possession of others, such as Infour; or even choosing to manifest themselves at will in a certain way, such as Lord Enma and Toiletta. Also in the anime, some Yo-kai are made permanently visible due to the circumstances of their death or the origins of their Yo-kai conversion, such as Pandanoko, Manjimutt and Snartle.
Most of them being based on the actual youkai and other mythological entities from traditional folklore and even certain fictional characters from popular culture, most Yo-kai have unusual body compositions, such as being single- or multi-eyed or even multi-limbed; others may be based on inanimate objects, which are known under a sub-category of Yo-kai known as Tsukumogami (Japanese: 付喪神) or even food, also ranging from being based on animals like mammals, birds, fish or insects and even more traditional demons or mythical creatures.
Many Yo-kai used to be humans, such as Frostina/Blizzaria, Hungramps, Spoilerina and Venoct; animals, such as Cricky, Usapyon, Tomnyan and Jibanyan; or even inanimate objects, such as Wazzat, Dummkap and Brokenbrella. Though the process for becoming a Yo-kai is largely unknown, most Yo-kai develop an attachment to an important place or part of their previous lives, with some having unsettled business to fulfill; however, doing so does not make them pass to the other side.
Though most Yo-kai cannot die in the strictest sense of the word, they can have their Soul Gems forcefully removed, leaving an empty shell behind. The "death" can be reversed by returning their souls, however. Those who can or are able to die simply have a supernaturally long life span. It was also revealed that some Yo-kai can in fact be exorcised and sent to the other side. Some Yo-kai do have the ability to die but it depends on who and the circumstances.
It is not yet clear when the first Yo-kai came into existence, though several of them were around since the Sengoku period and Edo period. A group of earlier Yo-kai, known as the Classic Yo-kai, existed at least 60 years prior the start of the series, along with other Yo-kai which can also be found in the present, with others being encountered only in certain time periods. Likewise, Merican Yo-kai can be found in St. Peanutsburg, BBQ, implying that other areas of the world have their own individual Yo-kai, not just Japan.
Tribes of Yo-kai
- Main article: Yo-kai Tribes
Originally, every kind of Yo-kai were divided into the eight main tribes: Brave, Mysterious, Tough, Charming, Heartful, Shady, Eerie and Slippery. In the video games, each of the tribes has their own strengths and rarities, and if two or more Yo-kai of the same tribe are adjacent to each other, they will receive a Tribe Unity bonus. In Yo-kai Watch 2, the Wicked were introduced, consisting of the Wicked Executives and the Wicked Servants. In Yo-kai Watch 3, the Hagure debuted as the 10th main tribe with Android Yamada being the first from the tribe to officially be revealed so far, and the Yo-kai Watch Busters subseries introduced the Enma. Every tribe has their own summoning unique chant when a Yo-kai from that tribe is summoned.
- Present Yo-kai (Japanese: イマドキ妖怪 Imadoki Yōkai): is an un-official name giving to Yo-kai who hail from the present day of Japan in time within the Yo-kai Watch series, given this name retroactively following the release of Yo-kai Watch 2 and the Classic Yo-kai.
- Rare Yo-kai (Japanese: レア妖怪 Rea Yōkai): are a select group of Yo-kai that are typically difficult to encounter and befriend, and some can (additionally or exclusively) be freed from the Crank-a-kai, while others need an item pulled from the Crank-a-kai to make them appear in the overworld. A good number of Rare Yo-kai, especially those of which that originated in Yo-kai Watch, are color-swapped versions of other, more commonly found Yo-kai.
- White Yo-kai: are a type of Yo-kai found in Yo-kai Watch. They are regular or hard-to-find Yo-kai under the influence of McKraken. They appear in both the Yo-kai World and Springdale but cannot be befriended due to being controlled by McKraken's anti-human propaganda.
- Classic Yo-kai (Japanese: 古典妖怪 Koten Yōkai): Yo-kai introduced in Yo-kai Watch 2: Bony Spirits and Fleshy Souls which are wholly based on the youkai of classic Japanese mythology. They can only be found in the past.
- Local Yo-kai (Japanese: ご当地妖怪 Gotochi Yōkai): are a group of Rare Yo-kai which debuted in Yo-kai Watch 2.
- Gotochinyan (Japanese: ご当地ニャン Gotōji nyan): are a group of Local Yo-kai exclusive in Yo-kai Watch World.
- Commander Yo-kai (Japanese: 武将妖怪 Bushō Yōkai): are Yo-kai themed after the major players of the Romance of the Three Kingdoms epic. They appear in Yo-kai Sangokushi.
- 'Merican Yo-kai (Japanese: メリケン妖怪 Meriken Yōkai): Yo-kai introduced in Yo-kai Watch 3: Sushi and Tempura. As the name implies, they are from America. They are considered a subgroup of Present-Day Yo-kai.
- Deva Yo-kai (Japanese: 神妖怪 Kami Yōkai): are a select group of powerful Yo-kai that are introduced in Yo-kai Watch 3, following the 2.0 Update and the release of Sukiyaki.
- Kuroi Yo-kai (Japanese: 黒い妖怪 Kuroi Yōkai):
- Goku Yo-kai (Japanese: 極妖怪 Goku Yōkai): are a set of 5 Yo-kai introduced in Yo-kai Watch: Wibble Wobble. They are SSS Rank Yo-kai of various tribes under the control of Rinne.
- Treasure Yo-kai (Japanese: 秘宝妖怪 Hihō Yōkai): are a select group of powerful Yo-kai that are introduced in Yo-kai Watch 3, following the 4.0 Update. Much like the Mystery Legendary Yo-kai, the Treasure Yo-kai are powerful Yo-kai that are based on civilizations in antiquity.
- Kenbumajin (Japanese: 剣武魔神 Kenbumajin) Yo-kai: are Yo-kai introduced in Yo-kai Watch Shadowside. They're of the same status as the Genjuu.
- Genjuu (Japanese: 幻獣 Genjuu) Yo-kai: are Yo-kai introduced in Yo-kai Watch Shadowside. They're of the same status as the Kenbumajin.
- Legendary Yo-kai (Japanese: レジェンド妖怪 Rejendo Yōkai, Legend Yo-kai): A group of powerful Yo-kai that can only be befriended after filling out the Legend Pages in the Yo-kai Medallium, which is done by collecting certain sets of Yo-kai Medals to break the seal surrounding a specific Legendary Yo-kai, with each seal requiring a different set of Yo-kai. Like every Yo-kai, a Legendary Yo-kai falls under one of the tribes. Unlike every other kind of Yo-kai that from their respective tribes, Legendary Yo-kai's summoning chant are very unique, bombastic and grandiose.
'Merican Legendary Yo-kai
- 'Merican Legendary Yo-kai (Japanese: メリケンレジェンド妖怪 Meriken Rejendo Yōkai, Merican Legend Yo-kai): A group of Legendary Yo-kai from America, like 'Merican Yo-kai, introduced in Yo-kai Watch 3.
Legendary VIP Yo-kai
- Legendary VIP Yo-kai (Japanese: 偉人レジェンド妖怪 Ijin Rejendo Yōkai, Great Legend Yo-kai): A special group of Legendary Yo-kai in Yo-kai Watch 3, who were originally famous people before their death. Notably, all of them sport a five-pointed sheriff-like star with the kana イ, meaning "I", which stands for "Ijin" (偉人, kanji for "Great Man").
Commander Legendary Yo-kai
- Commander Legendary Yo-kai (Japanese: 武将レジェンド妖怪 Bushō Rejendo Yōkai):
Mystery Legendary Yo-kai
- Mystery Legendary Yo-kai (Japanese: ミステリーレジェンド妖怪 Misuterī Rejendo Yōkai, Mystery Legend Yo-kai) are a special class of Legendary Yo-kai debuting in Yo-kai Watch 3. Many of the Yo-kai in this group are based on ancient civilizations, with a large number of Mystery Legendary Yo-kai having Egyptian themes.
Crystal Legendary Yo-kai
- Crystal Legendary Yo-kai (Japanese: Cレジェンド妖怪 Kurisutaru Rejendo Yōkai) are Legendary Yo-kai introduced in both Yo-kai Watch Busters 2 and Yo-kai Watch: Wibble Wobble. These Legendaries are basically the Gemnyan equivalent of the first 8 Legendary Yo-kai.
- Boss Yo-kai (Japanese: ボス妖怪 Bosu Yōkai): Yo-kai are powerful enemy Yo-kai which the player cannot befriend or recruit, and are typically stronger than most Yo-kai the player has met up to that point.
- Yo-Criminals (Japanese: 指名手配妖怪 Shimeitehai Yōkai): also known as Wanted Yo-kai, are a group of Yo-kai which cannot be befriended, and instead must be fought and captured for a crime they committed, which mostly all revolve around vandalism and disrupting the peace. They are notable for all being color variations of normal Yo-kai.
The Yo-kai Watch
Models of the Yo-kai Watch
- Main article: Yo-kai Watch (item)
The Yo-kai Watch (Japanese: 妖怪ウォッチ Yōkai Wotchi) is a device that allows the humans to see and communicate with Yo-kai; the Yo-kai can also communicate with humans.
Yo-kai Watch Model Zero
The Yo-kai Watch Model Zero (Japanese: 妖怪ウォッチタイプ零（ゼロ）式 Yōkai Wotchi Taipu Zero-shiki lit. "Youkai Watch Type Model Zero") debuted in Yo-kai Watch 2 and is a model that was invented 60 years ago, marking it as the first usage of the Yo-kai Watch. Both Z and Classic Medals are used for this model.
Yo-kai Watch Model U
The Yo-kai Watch Model U (Japanese: 妖怪ウォッチＵ（ユー） Yōkai Wotchi Yū) debuted in Yo-kai Watch 3 and is a model that both U and 'Merican Medals are used with, but is still compatible with all previous medals.
Yo-kai Watch Dream Model
The Yo-kai Watch Dream Model (Japanese: 妖怪ウォッチドリーム Youkai Wotchi Doriimu) debuted in Yo-kai Watch 3 and is a model for which the Dream Medals are used.
Kuroi Yo-kai Watch
The Black Yo-kai Watch (Japanese: 黒い妖怪ウォッチ Kuroi Yōkai Wotchi) seems to only appear in an alternate world (known as the Dark World). Its creator is unknown. This model is unique in that instead of searching for Yo-kai, its light (purple in color) scans a human and causes a being sealed in the watch to swallow the human whole, after that it spits him/her out transformed into a Yo-kai.
Yo-kai Watch Elda
Yo-kai Watch Ogre
The Yo-kai Watch Ogre (Japanese: 妖怪ウォッチ オーガ Yōkai Wotchi Ōga) allows the user to transform into one of 4 chosen Genma Yo-kai from the watch by pressing the button on the side and rotating the dial to the specific spot. Pushing the center of the watch down would allow the user to transform into the selected Yo-kai in battle. Also, It has the power to summon Kenbumajin Yo-kai by inserting their respective Youseiken, such as when the Fudou Raimeiken is inserted into the watch, the user will transform into Fudou Myouou.
Yo-kai Watch Animas
Yo-kai Watch Elda K
- Main article: Yo-kai Medals
Yo-kai Medals (Japanese: 妖怪メダル Yōkai Medaru) are small coin-like trinkets used to summon Yo-kai through the Yo-kai Watch, as they normally give the medals as a sign of friendship. Some Yo-kai who have the original medals are usually silver, and used for the original model of the watch. A Legendary Yo-kai's Yo-kai Medal is identified dominantly by the color gold.
The Classic Medals (Japanese: 古典メダル Koten Medaru) are red Yo-kai Medals from Classic Yo-kai and are used with the Model Zero of the Yo-kai Watch.
The 'Merican Medals (Japanese: メリケンメダル Meriken Medaru) are vibrant-red Yo-kai Medals from 'Merican Yo-kai and are used with the Yo-kai Watch Model U.
The B-Medals (Japanese: Ｂメダル Bī Medaru) are Similar to the Z and U Yo-kai Medals, it features a distinctive marking in the upper right corner of 4 specific kanji, which vary depending on what that Yo-kai's role is as a Blaster: Attack (Japanese: 攻 Kō) for Fighters, Heal(Japanese: 治 Ji) for Healers, Odd (Japanese: 奇 Ki) for Rangers, and Protect (Japanese: 守 Shū) for Tanks. The kanji, much like the names, are written in a calligraphic font. The role of a Yo-kai as a Buster also influences the inner frame's color: Red for Attackers, Green for Healers, Purple for Rangers, and Dark Blue for Tanks. There are also B Medals that depict Boss Yo-kai. The B Medals that have Boss Yo-kai on them are known as Boss Medals (Japanese: ボスメダル Bosu Medaru).
The Sangokushi Medals (Japanese: 三国志メダル Sangokushi Medaru)
The Uta Medals (Japanese: うたのメダル Ūtamedaru) are known to be a special variation of Yo-kai Medals. Unlike other medals, some of them are known to contain multiple Yo-kai and they sing a song while they get summoned.
The Dream Medals (Japanese: ドリームメダル Dorīmu Medaru) are poker chip-like Yo-kai Medals, which a few Merican Yo-kai have and are used with the Yo-kai Watch Dream Model.
The Kuroi Medals (Japanese: 黒井 メダル Kuroi Medaru) are another special variation out of the Medals. They are known to have come from another dimension, where Yo-kai are a lot more scarier. They only work on the Kuroi Yo-kai Watch or the Yo-kai Watch Dream Model.
The Treasure Medals (Japanese: トレジャーメダル Torejā Medaru) are Yo-kai Medals that taken on the form of treasure coins.
- Main article: Yo-kai Arks
- Main article: Youseiken
List of Yo-kai in the Yo-kai Medallium in the main Yo-kai Watch games
- List of Yo-kai by Medallium Number (Yo-kai Watch)
- List of Yo-kai by Medallium Number (Yo-kai Watch 2)
- List of Yo-kai by Medallium Number (Yo-kai Watch 3)
- Most promotional outlets usually type out the English spelling as "Yo-Kai" or "Yokai", which is the incorrect way to spell out the word.