Yōkai and Obake

Yōkai (妖怪^?, ghost, phantom, strange apparition) are a class of supernatural monsters in Japanese folklore.

Yōkai range eclectically from the malevolent to the mischievous, or occasionally bring good fortune to those who encounter them. Often they possess animal features (such as the Kappa, which is similar to a turtle, or the Tengu which has wings), other times they can appear mostly human, some look like inanimate objects and others have no discernible shape.  

Yōkai usually have a spiritual supernatural power, with shapeshifting being one of the most common. Yōkai that have the ability to shapeshift are called obake.
 
Obake (お化け^?) and bakemono (化け物^?) are a class of yōkai, preternatural creatures in Japanese folklore. Literally, the terms mean a thing that changes, referring to a state of transformation or shapeshifting.

As a secondary usage, the term obake can be a synonym for yūrei, the ghost of a deceased human being.^[2]

A bakemono's true form may be an animal such as a fox (kitsune), a raccoon dog (tanuki), a badger (mujina), a transforming cat (bakeneko), the spirit of a plant — such as a kodama, or an inanimate object which may possess a soul in Shinto and other animistic traditions. Obake derived from household objects are often called tsukumogami.