Yokai are those creaturs such as a kappa, a long-nosed goblins and ogres.
Animals holding supernatural powers such as the fox, a raccoon dog, snake and cat disappeared from the list after the Japanese economic boom.

Or, they may be mysterious, strange things.For instance they can be sounds, smells, appearance traits, and such combinations.
Ancient people thought that the soul stayed in all things.
They called these "MONONOKE(Disregarded it)", "(BAKEMONO)Making disregarding thing", and "Things that changed and become devilish", and feared it.

Moreover, it was thought that mysterious things for instance a creepy sound, a fishy smell, or a grotesque appearance
type were acts of those creatures.
Generally, they were called, "Yokai".