This butterfly has such a beautiful name = “angled sunbeam” in English and ura-gin-shijimi in Japanese (where gin means silver). The underside of the wings are a silvery white and the topsides are brown and white for females and brown and orange for males. [The photos show a female specimen].
Curetis acuta paracuta
angled sunbeam butterfly = ura-gin-shijimi
Location: Sweet chestnut grove at the edge of Fureiai-no-mori in Munakata (map)