File:SekienIkiryo.jpg
The ikiryō as illustrated by Toriyama Sekien.
In Japanese mythology, an ikiryō (生霊?) (also read shōryō, seirei, or ikisudama) is a manifestation of the soul of a living person separately from their body.
Origin
Traditionally, if someone holds a sufficient grudge against another person, it is believed that a part or the whole of their soul can temporarily leave their body and appear before the target of their hate in order to curse or otherwise harm them.
Souls are also believed to leave a living body when the body is extremely sick or comatose; such ikiryō are not malevolent.