Ippon-datara is a specter of Japan, living in the mountains of Kumano (Wakayama Prefecture) and other areas. It has one eye and one leg.
In Hatenashi mountain range which is the boundary of Wakayama Prefecture and Nara Prefecture, it allegedly appears only on December 20. The day has been called 'Hate no Hatsuka' (20th day of the end) and considered as an evil day. Someone says that the mountain range's name 'Hatenashi' (no end) originated from 'Hate no Hatsuka' on which nobody had gone into the mountains.
Likewise, it has been said that if a person goes into Mt. Obagamine on December 20, he/she would encounter Ippon-datara. It is advised not to enter the mountain on that day. In this area, Ippon-datara has been considered to be like a telephone pole with an eye (or eyes) and a nose. It is also said that the specter leaves footprints of one leg, looping the loops on a snowy day. Moreover, Ippon-datara of Mt. Obagamine sometimes refers to a fierce god called Inosasa-o (King Inosasa) which is transformed from the spirit of a wild boar. Inosasa-o had been terrifing people for eating travelers. However, after a high priest did kanjo (praying for a coming of a deity), Inosasa-o gave up such acts of appalling cruelty. However, it is said that Inosasa-o becomes free once a year, on December 20.
Although there are many legends that Ippon-datara attacks people, it is said that it never attacks a mailman for unknown reasons.
Datara' of Ippon datara may have come from Tatara-buki (blacksmith). Someone says it is because in the past the heavy labor of blacksmiths had weakened their one eye and one leg; other says it is because Ippon-datara had appeared near the remains of mines (refer to myths of single eye and single eye in legends). Someone says that it is Ame no Mahitotsu no Kami, the one-eyed god of smith, who ruined himself.
In spring of 2004, one-legged footsteps were fond in an area called Tomida in Tanabe City, Wakayama Prefecture. It was called 'Tomita no Gashanbo' (ghost with one leg). It became the center of attention for a possible revival of Ippon-datara or Gashanbo.
Since 2005, 'Ippon-ashi-datara Kokeshi' (wooden doll of ghost with one leg), a folk craft made by referring to the folklores of Ippon-datara, is sold at Matsumoto Kobo Craft Center in Yoshino County, Nara Prefecture. Someone says that it is an excellent souvenir as a doll in the shape of a specter.
Moreover, in Kaminikawa County (present Toyama City) of Toyama Prefecture, and in Hida region of northern Gifu Prefecture, and in Tsukubo County of Okayama Prefecture, remain legends of Yuki-nyudo; it has been considered to be a snow monster with a bald head, and has one eye and one leg, and its footstep it leave on the snow is thirty centimeters long. However, since it has the same characteristics as Ippon-datara, they are regarded as the same and one specter in some literatures.