Chionographis japonica Maxim.

in Japan, Awaji Island, May 2008 (pictures 1, 3 & 4)
in Japan, Honshu, Mt. Rokko, May 2008 (picture 2)
in Japan, Honshu, Nikko, June 2010 (picture 5)

Description in Bull. Acad. Petersb. xi. (1867) 436