The kudan is a yōkai of a "prophecy beast" type, whose news or urban legend has been disseminated in Japan since the Edo Period.
The kudan of "Mount Kurahashi", Tango Province. A kawaraban dated Tenpō 7 (1836). — woodblock-printed (on wood), in the collection of the Tokugawa Institute for the History of Forestry [ja].
The kutabe allegedly was spotted in Mount Tate, Toyama (Hirokata zuihitsu).
Nijigahara Holograph is a Japanese seinen manga series written and illustrated by Inio Asano. It is about the events that occur after a girl is thrown into a well by her classmates and their lives afterwards. The manga was serialized in Ohta Publishing's Quick Japan magazine from 2003 to 2005. It is licensed in North America by Fantagraphics Books.
The cover of Nijigahara Holograph, featuring butterflies fluttering past long grass
Asano at Toronto Comic Arts Festival 2018, holding a copy of the Fantagraphics translation of the manga