Residential Onsen Shuseikan

An old-fashioned inn at the far end of Akiyama-go, one of Nagano's most remote valleys. The mixed outdoor bath has a direct view of Mount Naeba, and the water itself is the real attraction: a sodium-calcium chloride-sulfate spring that shifts colour with the weather, running clear, milky white, or emerald green depending on the day. Floating mineral threads (yubana) drift through the tub, a sign of untouched spring water.