Public bathhouse · Open
Sunayu
- Day-use bathing
- Yes
- Fee
- ¥0checked 2026-10-09
- Hours
- 24時間checked 2026-10-09
Photo information
Save to passport
Official classification
Spring type (therapeutic classes)
Official spring-type name (as recorded)Alkaline simple hot spring (hypotonic, alkaline, high-temperature)
- Source temperature
- Unconfirmed
- pH
- 9.23
- Flow rate
- 6,000 L/min
- Radon
- Unconfirmed
Appearance & feel
Water colour · Feel
Unconfirmed
Colour and feel are listed only where a source states them. They vary by day and by bath.
What makes it special
Right beneath the dam wall, water rises through the riverbed into a bath that is free, open all night, and open to anyone. It is also mixed-gender, with nothing more than a simple changing hut.
Facilities in this area
Facilities come from the register (Wikipedia, OpenStreetMap, official sites). Those marked "natural spring unconfirmed" are listed on the basis of their name only.
Day-use bath · Open
Yumoto Onsen-kan
- Day-use bathing
- Yes
- Fee
- ¥800checked 2026-10-09
- Hours
- 10:00–21:00checked 2026-10-09
Baths2
| Type | Gender | Source | Bath temperature | Free-flowing | Added water | Heated | Recirculated | Disinfected |
|---|---|---|---|---|---|---|---|---|
| Indoor bath | Separate | Source welling beneath the building | Unconfirmed | Unconfirmed[4] | Unconfirmed[4] | Unconfirmed[4] | Unconfirmed[4] | Unconfirmed[4] |
| Private bath | Mixed | Unconfirmed | Unconfirmed | Unconfirmed[4] | Unconfirmed[4] | Unconfirmed[4] | Unconfirmed[4] | Unconfirmed[4] |
Getting there
Reachable by public transport
From JR Chugoku-Katsuyama Station on the Kishin line, about 35 minutes on the Maniwa community bus bound for Hiruzen Highlands to the 'Yubara Onsen' stop, then about 10 minutes' walk to Sunayu. By car about 5 minutes from the Yubara exit of the Yonago Expressway.
- Getting there
- Chugoku-Katsuyama Station · 35
- Through the year
- Snow in winter; at Sunayu the gap between water and air is large and you chill quickly on getting out
- Checked
- 2026-10-09
About the water
Yubara's water is an alkaline simple spring; the tourist centre's site gives pH 9.4 (our ledger's Wikipedia-derived 9.23 may be from a different analysis). It is low in minerals and strongly alkaline, the type that leaves skin feeling slippery. At Sunayu the water rising through the riverbed simply fills the three pools and cannot be regulated; the upstream pools are hotter, and the etiquette page warns of the gap between water and winter air. In town, the Yumoto Onsen-kan bathhouse sits over a source welling from beneath the building. Wikipedia gives estimates of source numbers and flow, unconfirmed.
| Source | Source temperature | pH | Radon | Checked |
|---|---|---|---|---|
| Yubara Onsen (tourist centre figure) | Unconfirmed | 9.4 | Unconfirmed | no check date |
Three things not to miss
Photo information
Sunayu
On the Asahi riverbank directly below Yubara Dam Three open-air pools fed from the riverbed, Bijin-no-yu, Kodakara-no-yu and Choju-no-yu, each a different temperature; etiquette is to start at the lowest, coolest pool and move upstream to the hottest. Free, 24 hours, closed Wednesday mornings for cleaning. 50-space municipal car park. Maintained by local residents.
Ranked 'West Yokozuna' in critic Noguchi Fuyuto's 1977 open-air bath rankings (Wikipedia). There are no lockers and no attendant; bathe as a guest in the townspeople's bath.[1][2][5]
The bathing garment as an answer
At Sunayu, the tourist information centre and the inns At the mixed Sunayu, women are encouraged to wear a rental bathing garment or wrap a towel, and men wrap towels too. Swimwear is allowed, ordinary clothes are not. Garments cost 2,000 yen for day visitors (1,000 refunded on return) or 500 yen through the inns; they are said to have been developed by the inns' proprietresses with a lingerie maker.
Yubara's practical answer to the problem that mixed baths exclude women in practice; a case study for the future of Japan's remaining mixed open-air baths.[1][2][3]
Photo information
The town of the hanzaki
The spa town and the Hanzaki Centre 'Hanzaki' is the local name for the giant salamander. The spa has a Hanzaki Centre, and in early August the Hanzaki Festival parades enormous salamander floats through the streets.
Hot spring and clear-river creature share one festival; the river that feeds Sunayu is the salamander's river too.[5]
The story
Bath licences and the Daisen cattle fair
Yubara lies on the upper Asahi river in Maniwa, Okayama. Legend says the monk Shoku was cured here in the Heian period (Wikipedia), and with Yugo and Okutsu it forms the 'three baths of Mimasaka'. In the Edo period thirteen baths lined the river, run by inns holding 'yukabu' licences that collected bathing fees. During the spring-to-autumn cattle and horse fairs at Mt Daisen the inns were so full the season was called 'the great lodging'. In the late Meiji era railways and rival resorts drew visitors away, and Yubara returned to being a quiet toji spa.[7][5]
The yokozuna beneath the dam
Yubara Dam was completed in 1955, and the bath left on the riverbank directly below it is Sunayu. Water rising through the riverbed fills three pools, free and open around the clock, kept by local residents. In 1977 the critic Noguchi Fuyuto placed it as 'West Yokozuna' in his national open-air bath rankings, and it has been 'the yokozuna's bath' ever since. There are no lockers, no attendant, no way to adjust the temperature; the tourism bureau asks visitors to remember that this is a residents' bath opened to them, not a tourist attraction.[1][3][5]
Keeping mixed bathing alive
Sunayu is mixed-gender and visible from the bridge and road. To make it usable for women, Yubara introduced bathing garments. The tourism bureau asks women to wear a rental garment or a towel and men to wrap a towel; swimwear is allowed, street clothes are not. Day visitors rent garments at the information centre or Yumoto Onsen-kan for 2,000 yen (1,000 refunded), overnight guests for 500 yen at their inn. Etiquette: wash at the downstream outlet, then move from the cooler pool up to the hot one. The rules also warn of theft and voyeurism, so bring nothing valuable.[1][2][3]
Going solo
Easy for solo travellersUnconfirmed
Weekend / peak restrictionsUnconfirmed
Where to eat dinnerRestaurants and izakaya in the spa; they close early
Private bathYes
checked 2026-10-09
Through the year
Recommended months
JanFebMarAprMayJunJulAugSepOctNovDec
Months open
JanFebMarAprMayJunJulAugSepOctNovDec
"Recommended" and "open" are recorded separately. Check the season for seasonal springs.
Aug — Hanzaki Festival in early August: giant-salamander floats and lanterns parade through the spa
Oct · Nov — Autumn colour along the Asahi river; the open-air season
Dec · Jan · Feb — Sunayu in the snow, but beware the cold on getting out
Food, culture & experiences
Yubara Dam
Towers directly over Sunayu; the reservoir is Lake Yubara[1]
Directly above SunayuHanzaki Centre
A centre where you can see giant salamanders (Wikipedia)[5]
Within the spaYakushi-do hall
In the centre of the spa; hot water wells beside the hall, and local belief says lost things come back (prefectural association)[6]
About 5 minutes' walk from the bus stopEditors' guide
Take the bus from Chugoku-Katsuyama to Yubara Onsen. Rent a bathing garment and warm up at Yumoto Onsen-kan (closed Wednesdays), then visit Sunayu at a quiet hour, early morning or dusk. Rinse at the downstream end and work up from the coolest pool. Leave valuables at your inn; there are no lockers. In early August, time your visit for the Hanzaki Festival.
The "editors' guide" above is written by the editors from sources; it is not a visitor's opinion.
Photo gallery
Visitor reviews
No reviews yet. While the review platform is being prepared, we do not display fictional reviews or ratings.
Review posting is in preparation, with visit date, facility, comments on water, scenery and access, photos, language and reporting.
Onsen areas nearby
.jpg){kind=link}
Unconfirmed & notes
- Pool temperatures at Sunayu and the number and flow of sources (Wikipedia estimates about 6,000 L/min) are unconfirmed; pH differs between the tourist centre (9.4) and the ledger (9.23)
- The tourist centre's etiquette page says garments or swimwear became mandatory in 2026, while the Maniwa tourism bureau page says 'recommended' for women and towels for men; check the notice on site
- Exact Hanzaki Festival dates, solo-stay terms and bus frequency/fares are unconfirmed
Sources
- 湯原温泉 砂湯 - 真庭観光局(真庭観光WEB)一般社団法人真庭観光局 · 2026-10-09
- 湯原温泉砂湯 - 岡山観光WEB公益社団法人岡山県観光連盟 · 2026-10-09
- 砂湯の入浴作法・なぜ横綱なのか - 湯原観光情報センター湯原観光情報センター(yubara.com) · 2026-10-09
- 湯本温泉館 - 真庭市真庭市 · 2026-10-09
- 湯原温泉 - WikipediaWikipedia · 2026-10-09
- 湯原温泉 薬師堂 - 岡山観光WEB公益社団法人岡山県観光連盟 · 2026-10-09
- 湯原温泉の歴史 - 湯原観光情報センター湯原観光情報センター(yubara.com) · 2026-10-09
Register sources
- 湯原温泉 - Wikipedia(日本語版)Wikipedia · CC BY-SA 4.0 · 2026-10-09
- Wikidata Q11563486Wikidata · CC0 · 2026-10-09
Data status
Name & locationPublishedCoordinatesPublishedSpring typePublishedPhotosPublishedFacilitiesPublishedVisiting info (dated)PublishedEditorial articlePublished
Updated 2026-10-09
Suggest a correction or addition