The 1,300-year-old birthplace of Nasu Onsen. Inside the wooden bathhouse, tubs are graded from 41 to 48°C, all fed with milky, strongly acidic sulfur water. No showers, no soap — start with the traditional head-dousing ritual.
A day-use facility on the same source as Shika-no-yu, open every day until 9 pm with an open-air bath and private rooms. Ideal for families or anyone daunted by Shika-no-yu's rituals — the milky water is identical.
A lone inn at 1,300 m, the last stop in the Nasu hot-spring range. Spring water gushes out behind the building in such volume that it forms a river, dammed into the vast outdoor 'Kawa-no-yu' — nothing else like it in Japan. Mixed bathing since the inn's founding, but bathing wear is included so beginners can relax. Day use is limited to three hours (reception 11:30–14:30), ¥1,300 with face towel and bathing wear. The outdoor bath closes in bad weather or for cleaning, so phone ahead. Autumn colour and snow seasons are the draw.