Onihitokuchi

Onihitokuchi is not a single originating mythic biography but a recurring narrative motif found across Heian-era setsuwa collections (such as The Tales of Ise, Nihon Ryōiki, and Konjaku Monogatarishū). In these tales an oni from the non-human realm intrudes into the human world—often at night or during liminal circumstances—and immediately consumes a person. Later commentators and illustrators (for example, Edo-period yōkai compilers) treated the motif as a recognizable example of oni activity and the compound word came to be used idiomatically to denote great danger or an act completed in one swift motion.

Source tales treat the agent as an oni, and Edo-period illustrators have depicted the motif under the title onihitokuchi, but the supplied sources do not give consistent, specific bodily details (such as color, horn number, or exact size). Descriptions in the cited setsuwa emphasize the act (a person being eaten in one mouthful) and sometimes note that the oni may appear as a human or be concealed in a place (for example, living in a cellar).

In the source material the primary characteristic is the narrative act: an oni devours a person in a single mouthful. Tales also repeatedly show deceptive interaction modes—an oni may present as a human suitor or be a hidden inhabitant of a space (a cellar) who suddenly takes and eats a person. The motif is also used figuratively to explain sudden deaths, disappearances, or catastrophic human loss, per interpretive theories recorded in later commentary.