Onryō.

Onryō (怨霊, おんりょう) does not begin as a single visual monster. In the oldest records it is known through effects, illness, disaster, political collapse, and uncanny vengeance rather than through a fixed body. A court fears the dead because storms, deaths, and misrule seem to follow them. The onryō is therefore first a force of resentment felt in the world, not a neatly pictured ghost walking a corridor.

Only later, especially through Edo theater and ghost painting, does the figure become visually standardized. Then the onryō often appears in white burial robes, with long unbound black hair, pallid face, and the stillness of a dead body that refuses to stay gone. That image is powerful, but it is a later shorthand for a much older religious fear.

Onryō does not seek simple haunting. It seeks redress. A wronged dead person returns to break health, lineage, political order, or domestic peace until the injustice that produced the ghost is acknowledged. In aristocratic and court settings that vengeance can extend far beyond one personal enemy, touching rulers, ministers, and entire capitals through disease, fire, storm, or panic.

Because of that scale, the answer to an onryō is rarely just exorcism. Traditions of appeasement include prayer, ritual pacification, posthumous promotion, restoration of honor, and even enshrinement as a kami. The history of Sugawara no Michizane shows this especially clearly, where the fear of a wrathful dead man and the reverence paid to him become part of the same religious process.