Yo-kai are spiritual beings whose influence is responsible for every one of the strange, paranormal events in the human world. Most of these influences range for example, 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.
With some exceptions, most Yo-kai are invisible to humans without the Yo-kai Watch. In some cases, some Yo-kai can disguise as humans by putting a magical leaf on their heads, such as seen by Komasan and Komajiro in the anime, or by more conventional forms of shape-shifting, such as Kyubi. 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 Manjimutt or Snartle.
Most of them being based on the Yo-kai and other mythological entities from traditional folklore, most Yo-kai have unusual body compositions, such as being single-eyed or multi-eyed, or even multi-armed; others may be based on inanimate objects (which are known under a umbrella sub-category of Yo-kai known as Tsukumogami (Japanese: 付喪神)) or even food; ranging from being based on animals like mammals, birds fish or insects; and even more traditional demons or creatures from Japanese folklore.
Several Yo-kai used to be humans (such as Hungramps, Manjimutt or Venoct), animals (such as Cricky or Jibanyan), or even inanimate objects (such as Wazzat or Brokenbrella). Though the process for becoming a Yo-kai is largely unknown, most Yo-kai develop an attachment to an important place of their previous lives, with several having "unsettled business" to fulfill; however, doing so does not make them pass to the other side.
Though most Yo-kai, being technically ghosts, cannot "die" in the strict sense of the word, they can have their souls (Soul Gems) forcefully removed, leaving an empty shell behind. The "death" can be reversed by returning their souls, however. Those who can die simply have a supernaturally long life span.
It is not yet clear when were the first Yo-kai came into existence, though several of them were around since the Sengoku Period. Some Yo-kai, known as the Classic Yo-kai, can be found until 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 this time period. Likewise, Merican Yo-kai can be found in St. Peanutsburg, U.S.A., implying that other areas of the world have their own individuals of 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, and Slippery. In the video games, each of the tribes their own strengths and rarity, 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 be revealed so far. Every tribe has their own summoning chants when a Yo-kai from that tribe is summoned.
Types of Yo-kai
- Classic Yo-kai (Japanese: 古典妖怪 Koten Yōkai): Yo-kai introduced in Yo-kai Watch 2: Bony Spirits and Fleshy Souls wholly based on Yo-kai 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 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 8 required Yo-kai. Like every species of 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.
Great Legendary Yo-kai
- Great Legendary 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").
Yo-kai Models and Models of the Yo-kai Watch
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; Yo-kai can also communicate with humans. The basic model, from of the watch is.
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, is a model invented 60 years, making it the first usuage of the Yo-kai Watch. Z and Classic Medals are used for this model.
Yo-kai Watch U
Yo-kai Watch Dream
- Main article: Yo-kai Medals
The Yo-kai Medals (Japanese: 妖怪メダル Yōkai Medaru) are small coin-like medals used to summon Yo-kai through the Yo-kai Watch; Yo-kai 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. Legend Yo-kai's Yo-kai Medals are identified dominantly as the color gold.