Ikiryō

There is no single cosmogonic origin in the cited materials; rather, ikiryō emerges within a worldview—attested in Buddhist scripture references and Heian-period literature—where the human soul can detach from the living body (described with verbs such as akugaru, 'departure') and wander or manifest elsewhere. Classical tales (for example, The Tale of Genji's account of the ikisudama) and folktales present instances in which strong emotions (grudges, jealousy, love, or mōnen—wayward thoughts/obsessions) cause all or part of a living person's soul to depart and act independently.

Accounts show varied manifestations rather than a single fixed form: the ikiryō may appear as a visible personlike apparition (often resembling the originator), manifest as disembodied parts (e.g., a wandering severed head in Sorori Monogatari), be perceived only as sounds or presence (wailing behind closed gates in Konjaku Monogatarishū-type tales), or operate by inhabiting another person's body (possession, as in the Matsutōya tale where spirits spoke through a possessed boy). These forms are attested in literary and folkloric sources rather than described as uniform.

Sources attest that an ikiryō can leave a living person's body and travel across distances to haunt, possess, or afflict others. In tales it may cause illness and even death (Konjaku Monogatarishū), inflict tatari (curses) when motivated by vengeance (linked in sources to onryō-like activity), possess and speak through another person's body (Matsutōya Yūrei), act from love or infatuation, or appear as a portent shortly before the originator's death. The phenomenon is variable across accounts: sometimes malicious, sometimes non-vengeful, and often tied to the originator's emotional state.