Angelica (cf) longiradiata (Maxim.) Kitag. var. yakushimensis (Masam. et Ohwi) Kitag.

Family: Apiaceae
English: Wild celery sp.
Japanese: ヒナボウフウ(ツクシゼリ) [Hinabōfū/Tsukushizeri]

I was taught that these tiny little puffs like salt-and-pepper that can be found from Kosugidani Village to nearly the top of Nagata Daké are A. longiradiata (ツクシゼリ), but I have come across two names that indicate Yakushima variants or subspecies: A. Longiradiata var. yakushimensis (ヒナボウフウ) and A. yakusimensis (ヤクシマノダケ). I just have not had the time to research the differences, but perhaps that explains the oddly long blooming period. . .

References:
「BG Plants 和名－学名インデックス」（YList） 米倉浩司・梶田忠 (2003-)　，http://bean.bio.chiba-u.jp/bgplants/ylist_main.html（2014年10月13日）.
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13日）