I haven’t seen the book myself yet, but apparently I am on page 235 of the 2010 Ripley’s Believe it or Not Annual. http://ripleybooks.com/annuals/2010/extras/235 I must find myself a copy…
As indicated in the Hokkaido Snowy Mountain Guidebook (Hokkaido Yuki-yama Gaido – ISBN: 978-4894538047).
Difficulty as assessed by the Hokkaido Snowy Mountain Guidebook, p. 10 (Hokkaido Yuki-yama Gaido – ISBN: 978-4894538047). This overall index takes into account route-finding, altitude, ascent in vertical gain, time on the mountain, and technical aspects.