Viola biflora L.

Family: Violaceae
English: Alpine yellow violet
Japanese: キバナノコマノツメ (黄花の駒の爪) [Kibananokomanotsumé]

This species is commonly found throughout many mountainous regions in the northern hemisphere, but Yakushima is the only place in Japan where this violet lives south of Shikoku. It seems that it spread south during the last ice age, but died out in warm, southern regions, except Yakushima, where the tallest peaks in Kyushu remain cold enough to harbor this small, unassuming beauty.

It is not so common to find one in bloom here, and one never sees any of the large clumps as in photos from other parts of the world. Perhaps the deer are responsible.

References:
新版　屋久島の植物 川原勝征,初島住彦(監修),2001：南方新社
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）