Yokai (often spelled Youkai) ("apparitions", "spirits" or "demons") are class of creatures in Japanese folklore ranging from the evil oni to the mischievous kitsune. Yokai are generally more powerful than human beings, and because of this, they tend to act arrogantly towards mortals. Yokai also have different values from human beings, and when these conflict, it can lead to animosity. They are generally invulnerable to human attack, but they can be defeated by skilled yokai exterminators (taijiya) and Buddhist monks with Buddha's blessing or ofuda.
Some yokai simply avoid human beings and, thus, trouble; they generally inhabit secluded areas far from human dwellings. Other yokai, however, choose to live near human settlements out of a true liking of mankind. Some stories even tell of yokai breeding with human beings to produce han'yo, or "half-demons". Most of these tales begin as love stories, but they often end in sadness resulting from the many obstacles faced by yokai and mortals in such relationships.
Manga artist Shigeru Mizuki popularized many types of yokai in his works in the 1960's.
There are a wide variety of yokai in Japanese mythology. In general, they can be broken up into four categories based on their natures:
In general, yokai is a broad term, and can be used to encompass virtually all monsters and supernatural beings, even including creatures from Western mythology on occasion. This group is also referred to as "mononoke".
On the other hand, it is also used in a stricter sense to refer only to the natural, earthly beings of traditional Japanese folklore. These yokai are natural beings, much like animals. In fact, foxes were historically thought of as yokai, and are often presented as such in modern fiction. Unlike normal animals, however, they have strange powers or bizarre attributes, and tend to be more intelligent than regular animals, many of them being known as tricksters.
Some of the better known yokai include the following:
In addition to the previously mentioned mountain oni, there are demonic oni, a wide variety of creatures that inhabit Jigoku, the Buddhist hell.
Obake (also called bakemono or simply bake) are creatures that have changed from one form to another, generally becoming more powerful in the process. Usually this change is due to the presence of negative feelings, and as such, obake tend to be violent, or even malicious.
Yurei are ghosts or spirits, and tend to be similar to their western counterparts.