Nakaokogen Hotel Kazaguruma

Every room at Kazaguruma has its own private onsen bath, fed by spring water that comes from steam vents on nearby Mount Yakedake. Reviewers mention a real sulfur smell as the water runs into the tub, and opening the bathroom window wide gives something close to an open-air feel. There's no shared bathhouse on site: all bathing here happens privately, in the room. The hotel is small, 13 suite-style rooms, in Nakao, part of Okuhida Onsengo near Shinhotaka. Much of the staff comes from overseas and works in fluent Japanese, a mix guests note alongside the Hida-made furniture around the building. Up on the rooftop there's a deck for looking out at the mountains, and at the stars once the sun goes down.