Spiranthes sinensis (Pers.) Ames var. amoena (M.Bieb.) H.Hara

Family: Orchidaceae
Japanese: ネジバナ

This orchid pops up, almost like an annual weed, along the train tracks and elsewhere. But it's gone again before you know it!

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（ 2017年6月1日）.