Enkianthus campanulatus Nichols.

in Japan, Honshu, Rokko Alpine Garden, May 2008 (pictures 1, 2, 3 & 4)
in Japan, Honshu, Yunoko Lake, June 2010 (pictures 7 to 11)
in Japan, Honshu, Ofuna Botanical Garden, May 2008 (picture 12)