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.
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, technically being ghosts, 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.
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.
- 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.
- '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.
- 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").
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.
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.
- 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: 夢のメダル Yume no 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.
Treasure Medals (Japanese: Tメダル T Medaru) are Yo-kai Medals that taken on the form of treasure coins.
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.