Diplomorpha pauciflora (Franch. et Sav.) Nakai var. yakushimensis (Makino) T.Yamanaka

Family: Thymelaeaceae
Japanese: シマサクラガンピ (島桜雁皮) [Shima Sakura Ganpi]

According to [屋久島の植物?世界自然遺産の島], this species (or variety?) is restricted to Yakushima and a few other locations in Kagoshima. It looks like this variety was officially christened as recently as 1995. Often growing from rocky slopes, it gets to be a sizeable bush, lovely when covered with little yellow flowers.

References:
屋久島の植物?世界自然遺産の島 川原勝征，初島住彦監修,1995：八重岳書房
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）