right|thumb| from the 1776 book by [[Sekien Toriyama]]
, also known as , , or , is a disembodied spirit or ghost in Japanese popular belief and fiction that leaves the body of a living person and subsequently haunts other people or places, sometimes across great distances. The term(s) are used in contrast to , which refers to the spirit of those who are already deceased.
Summary
The popular belief that the human spirit (or soul) can escape from the body has been around since early times, with eyewitness accounts and experiences (hauntings, possessions, out-of-body experience) reported in anecdotal and fictional writings. of the living are said to inflict upon the subject or subjects of their vengeance by means of transforming into their form. It is believed that if a sufficient grudge is held, all or part of the perpetrator's soul leaves the body, appearing in front of the victim to harm or curse them, a concept not so dissimilar from the evil eye. The has even made its way into Buddhist scriptures, where they are described as "living spirits" who, if angered, might bring about curses, even just before their death. Possession is another means by which the Ikiryō are commonly believed to be capable of inflicting harm, the possessed person thought to be unaware of this process.