Yumotokan

Yumotokan draws its own sulfur spring on the grounds behind the ryokan, one of roughly forty sources scattered through Hirayu Onsen. The water is kept flowing fresh from that source and mixed with cool valley stream water to bring the heat down, arriving cloudy with bath flakes, sulfur-scented and faintly slippery on the skin. The indoor bath and the large open-air bath are connected, so you can drift between the two, and guests can also use three separate private open-air baths for free whenever they're unlocked: Ichii (一位) has the best view and blends into the natural surroundings, Sarasoju (沙羅双樹) sits beneath tall trees named for the tree in the Tale of the Heike, and Shirakaba (白樺) is built so you can bathe under an umbrella on a rainy or snowy day. The ryokan itself is an older wooden building with a hearth-lit lobby, irori (囲炉裏), where a fire crackles and, with luck, there's tea brewed over the coals.