Teshirosawa Onsen

Teshirosawa Onsen (手白澤温泉) sits at the deepest point of the Oku-Kinu (奥鬼怒) valley inside Nikko National Park, reachable only by a roughly two-and-a-half-hour hike from the Meotobuchi (女夫渕) trailhead. There is no shuttle and no day-use bathing, so the outdoor and indoor baths are shared only among the handful of overnight guests across six rooms. The water is a sulfury, free-flowing spring kept constantly fresh by kakenagashi (掛け流し), and the washing area itself runs on the same lukewarm overflow rather than a tap or shower. The open-air bath in the surrounding forest is a particular draw in winter, when steam rises against snow.