Daphne kiusiana Miq.

Family: Thymelaeaceae
Japanese: コショウノキ (胡椒の木) [Koshōnoki]

The flowers of this plant, which looks like it should be found in a garden, have a faint, sweet scent, although they are said to be poisonous.

References:
九州野山の花 片野田逸朗,2004：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）