Arisaema thunbergii Blume subsp. thunbergii

Family: Araceae
Japanese: ナンゴクウラシマソウ [(Nangoku) Urashima-sou]

The Japanese name for this arisaema comes from the fairytale of Urashima Taro, a fisherman who saved a sea turtle and was rewarded with a trip to the kingdom of the dragon god. The whip-like extension of the spadix is said to be reminiscent of his fishing line. According to Flora of Mikawa, subsp. thrunbergii has ripples at the bottom of the whip, while subsp. urashima is smooth, but I am just taking a guess until next year. . .

References:
九州野山の花 片野田逸朗,2004：南方新社
Flora of Mikawa (2019) http://mikawanoyasou.org/data/urasimasou.htm (Aug. 13, 2019)
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）