Yokai,The Ippondatara

 

The Ippondatara is a famous one legged Yokai that haunts the mountains of Japan.

In some villages, its  considered to be a cousin  to the kappa called gōrai who leave their river homes in in winter then transform from river yokai into mountain spirits called kashambo until they return to the rivers in spring. 

This one legged Yokai tends to keep to itself and is relatively harmless with the exception of December 20th, once per year on this day it turns very violent and will kill any human it encounters. 

. Those entering the mountains on December 20th and are unlucky enough to run into the ippondatara are immediately attacked and squashed squashed by  its powerful foot. Because of this, December 20th is considered an unlucky day in the areas where this yōkai lives and people (at least the  ones) stay out of the mountains on that day.

It's name comes from the man powered bellows that a blacksmith would use before the industrialization of the smithies shops  because this yōkai resembles a master blacksmith who lost the use of one eye from years of starting at the bright flames, and has one large leg from years of heavy work pumping the bellows.

It seems to prefer the mountains near Wakayama and Nara Prefectures (old Kii and Yamato Provinces), though it has also been sighted have other neighboring prefectures .

 Some believe it's possibly the ghost of a famous one-legged, one-eyed robber named Hitotsudatara who lived in the mountains of Wakayama and had supernatural strength.

Others think it may be a former mountain kami (God/powerful nature Spirit) that became  corrupted over time and transformed into a yōkai. The  one eyed appearance is a well known feature on  mountain spirits, and other one-eyed yōkai like the hitotsume kozō that was originally a mountain kami.