Hitotsume-nyūdō

Sources preserve multiple, locally specific etiologies rather than a single canonical origin. Kyoto tradition records some hitotsume-nyūdō sightings as actually kitsune in disguise; an Edo‑period kaidan picture records a tanuki taking the form to capture a character named Heitarō. Separately, a Mount Hiei tradition connects the figure to an older monkly yōkai called ichigan hitoashi hōshi (一眼一足法師, 'one‑eyed one‑footed hōshi'), preserved in a picture at Sōjibō on Enryaku‑ji, and presented in those accounts as an admonisher of monks who idled in training (linked in some versions to Ryōgen or his pupil Jinzen). These differing accounts—animal shapeshifter, transformed or admonishing monk, or autonomous yōkai—are attested in the collected sources as alternative local explanations for the same one‑eyed nyūdō appearance.

Hitotsume-nyūdō is described consistently as having the appearance of an ōnyūdō (the large monk/nyūdō form) but with only a single eye. Sources contrast it with the hitotsume-kozō (a one‑eyed child‑monk yōkai) to emphasize adult, tall, monklike morphology. Narrative sources include a Hidaka, Wakayama tale that depicts 'a large man with one eye' emerging from a splendid procession's palanquin and climbing a tree to attack an observer; visual and compendial sources from the Edo period also depict the form as that of an imposing monk‑figure in procession contexts.

Folkloric behaviors and capabilities attested in the sources include: appearing as part of spectacular processions that attract or surround travelers; physical expansion and contraction of height (likened to mikoshi‑nyūdō in compendia); climbing and attempting physical attack as in the Hidaka tale; and vanishing or dispersing when the apparition is threatened (the Hidaka story records the procession and figure disappearing when the young man threatened them with a sword). Several traditions attribute appearances to shapeshifting animals—kitsune (Kyoto) or tanuki (Edo kaidan picture)—or to monkly yōkai manifestations (ichigan hitoashi hōshi), so some sightings are interpreted as disguise rather than fundamentally distinct supernatural powers. Sources do not provide systematic magical abilities beyond these folkloric behaviors.