Rhododendron yakushimense (M.Tash. et H.Hatta) Craven

Family: Ericaceae
Japanese: ヤクシマヨウラクツツジ (屋久島瓔珞躑躅属) [Yakushima Yōrakutsutsuji]

This is one of the rarer species I've come across. An endemic species growing on cliff sides at higher altitudes, as recently as 2011 the genus was changed from Mensiesia (which includes 'false azaleas') to Rhododendron.

Formerly, Menziesia yakushimensis

References:
米倉浩司・梶田忠 (2003-)　「BG Plants 和名－学名インデックス」（YList），http://ylist.info（ 2019年8月14日）