Shibahara onsen - Kayanoya

A small ryokan tucked into the mountains of Oku-Chichibu, open since 1954 and a member of Nihon Hito wo Mamoru Kai (日本秘湯を守る会), the society for preserving Japan's secluded hot springs. The baths, both indoor and outdoor, are built from kaya (かや) wood, a slow-growing Japanese tree with a dense, smooth grain traditionally used for go boards. The spring water runs clear with a faint sulfur quality and is gently heated. Indoor and outdoor sets are gender-separated and swap sides at 22:00. No day use; overnight stays with in-room meals only.