What Are They?
The translation for the work Yōkai (妖怪) is something to the effect of “strange, supernatural creature or phenomena” in Japanese. The word is a combination of the characters 妖 (yō–attractive, bewitching, calamity) and 怪 (kai–mystery, wonder).
Over the years, different English words have been used in translation. Yōkai can be translated to monster, demon, spirit, or goblin, but it encompasses more. The term yōkai also includes ghosts, gods, transformed humans or animals, spirit possession, urban legends, and other strange phenomena. Nothing quite captures them in the English language. So Yōkai, like samurai, geisha, ninja, and sushi–is best used in its native language.
Determining what is or isn’t a yōkai is perhaps the most difficult aspect to a definition. Over the many eras of Japan’s history, different words have been used to describe supernatural forces perceived to be a part of the world. Words like bakemono, obake, mononoke, kaii, and oni have all been classified as yokai. Or alternatively, used to exclude such a creature from that category. This also begs the question can helpful spirits be yōkai or only evil spirits? Are kami yōkai? And are yōkai specific only to Japan?
Only in certain ways…
The penchant for mascots ranging from Pokémon to Miraitowa (ミライトワ) the official mascot of the 2020 Summer Olympics, is clearly a hold-over from the folk influences of yōkai and the Kami of Shinto belief. But the word “yōkai” is a Japanese transliteration or pronunciation of the Chinese term “yaoguai” who involve similarly strange creatures. Both languages use the same Chinese characters 妖怪, to describe them.
Whether you call them yōkai or yaoguai, they represent a broad and diverse class of ambiguous creatures in folklore and mythology across Asia. Defined by the possession of supernatural powers and by having attributes of the weird, the strange or the unnatural. They are especially associated with transformation and enchantment.
The broadest possible definition of yōkai includes all supernatural creatures and phenomena from all parts of the world. Essentially, everything supernatural everywhere on the Asian continent.