Tochigi · Nasu Onsen
Ōmaru Onsen Ryokan, Oku-Nasu (River Bath)
奥那須 大丸温泉旅館（川の湯）
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.
- Price (adult)
- ¥1,300
- Hours
- 11:30–15:00 (reception until 14:30)
- Closed
- Irregular (rotenburo closed in bad weather or for cleaning)
- Access
- About 60 min by Kanto Bus (for Nasu Ropeway) from JR Kuroiso or Nasu-Shiobara Station to Ōmaru Onsen; 30 min by car from Nasu IC
- Water type
- Simple spring
- Tattoos
- Ask ahead
- Admission
- Adults ¥1,300 / children (3 to elementary) ¥1,000, including a face towel and bathing wrap. Three-hour window only. Older sources quoting ¥1,000 are outdated
- Baths
- “Kawa-no-yu”: a cascade of large open-air pools formed by damming an actual river of hot-spring water from several private sources — mostly mixed (towels/wraps worn), with a women-only pool at the top. Separate indoor baths. The private “Oku-no-yu” is guests-only
- Water
- Sodium-chloride-bicarbonate type, rich in metasilicic acid — a moisturising “beauty bath”. Clear with a slightly slippery feel; the springs rise naturally right behind the inn
- Setting
- The innermost inn of the Nasu spa region, a lone lodge at 1,300 m on the flank of Mt Chausu. Member of the Japan Association of Secluded Hot Springs; 200+ years of history. Parking for 30; cards accepted
- Phone
- 0287-76-3050
- Official site
- www.omaru.co.jp/higaeri.htm ↗
- Open in Google Maps
- Google Maps ↗
Essentials
Stay in this onsen town
Compare and book stays in Nasu Onsen. Day bathing itself needs no booking.
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Why go
- Outdoor bath dammed from a hot-spring river
- Bathing wear included — easy first mixed bath
- Day use only 3 hours; call ahead
A river of hot water at 1,300 m: the “Kawa-no-yu”
Omaru Onsen Ryokan stands just below the Nasu Ropeway at 1,300 m, the highest and most remote inn in the Nasu spa region. Several private springs rise behind the inn and literally form a river of hot water; damming it with stones created the signature “Kawa-no-yu”, a staircase of open-air pools brimming with 100% source water, hotter at the top and gentler below. Mixed bathing has been kept since the inn’s founding, but towels or wraps are worn and the top pool is women-only, so it feels comfortable. Day bathing is a three-hour window, 11:30–15:00, and the ¥1,300 fee includes a towel and bathing wrap.
Tips & cautions
- Reception closes 14:30, out by 15:00 — arrive at 11:30 to make the most of it.
- The rotenburo closes in typhoons, heavy rain or snow, strong wind and for cleaning; mountain weather, so phone 0287-76-3050 first.
- Wear the supplied wrap in the mixed sections; women can happily stick to the top pool and indoor bath.
- At 1,300 m it is cool even in summer; in winter roads ice over and chains are needed. Combine with the Nasu Ropeway.
- Private bath is for overnight guests only. Drinking fountain available.
Getting there
Bus ~60 min from JR Kuroiso Station toward Nasu Ropeway to “Omaru Onsen”, right there (Yumoto 269). ~10 min by car from Nasu-Yumoto, ~40 min from Nasu IC. Free parking for 30; winter tyres essential.
Before you go
- No official tattoo policy is published — ask at reception.
- There is a mixed-gender area. Check the description for bathing garments and women-only hours.
- Ryokan day-use hours are limited and may be suspended in peak season — phone the same morning.
- Last entry is 30–60 minutes before closing.
Features
Mood & scenery
Price
Who with
Convenience
Amenities
✔ Verified operating: 2026-09 大丸温泉旅館公式 日帰り入浴ページ
Prices and hours change. Check official sources before visiting.
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Kojika-no-yu
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.
Kinugawa Onsen Niouson Plaza (day bathing)
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