Okayama · Hiruzen Highlands
Hiruzen Yatsuka Onsen Kaiyūkan
蒜山やつか温泉 快湯館
A day-use hot spring at the heart of the Hiruzen highlands in northern Okayama, 500–600 m up. Its great appeal is the open-air bath, where you feel the highland breeze and look out over Jersey-cattle pastures and the three Hiruzen peaks through the seasons — cool in summer, autumn colour, snow-viewing in winter. The alkaline simple water is gentle on the skin, and the facility covers the basics: main bath, jet bath, sauna and open-air bath. Adults ¥740, children ¥420; open 10:00–22:00 (until 21:00 December–March; last entry 30 minutes before), closed Wednesdays (next day if a holiday; open during Obon and Golden Week). About 20 minutes by car from Hiruzen IC or 60 minutes by bus from JR Chūgoku-Katsuyama Station. Combine with Hiruzen yakisoba, Jersey soft-serve and a drive toward Mt Daisen. 100 parking spaces.
- Price (adult)
- ¥740
- Hours
- 10:00–22:00 (until 21:00 Dec–Mar; last entry 30 min before closing)
- Closed
- Wednesdays (next day if a holiday)
- Access
- About 20 min by car from Hiruzen IC or Yubara IC; Maniwa community bus for Hiruzen Kōgen from JR Chūgoku-Katsuyama Station, about 60 min to 'Sports Center-mae' then 10 min on foot
- Water type
- Alkaline simple
- Tattoos
- Ask ahead
- Admission
- Adults ¥740, children ¥420, preschool children free. Discounts for Maniwa residents (ID) and for JAF or Montbell members or with an online discount screen shown — ¥600. Cash only. Towels sold or rented, shampoo provided, lockers. Rest room, shop. Sauna and plunge. Busy with skiers in the season (December–March)
- Baths
- A highland day-use onsen on the Hiruzen plateau (about 435 m) in Maniwa, Okayama — a semi-highland known for pasture, cycling and winter skiing. The heart is a rotenburo facing the three Hiruzen peaks and Mt Daisen, with a great bath, sauna and plunge. Adjoining the Hiruzen Kogen Centre, the cycle sports centre and the cycling paths, it is ideal for a soak after riding or trekking; in winter it fills with skiers from the Hiruzen Kogen ski area
- Spring water
- Hiruzen Yatsuka Onsen, a simple weakly radioactive cold-mineral spring (containing radon, of the alkaline family), colourless and light. Inhaling and bathing in radon is said to help gout, arteriosclerosis, high blood pressure and chronic skin disease. At 435 m the climate is cool, so you feel fresh even after a summer soak, and in winter the rotenburo amid snow mountains is superb
- Access & parking
- About 20 min from Hiruzen or Yubara IC on the Yonago Expressway, 1 h 40 min from Okayama city, 1 h from Yonago, 3 h from Hiroshima. From Chugoku-Katsuyama Station on the JR Hakubi Line, a bus to Hiruzen Kogen about 60 min to 'Sports Centre-mae' then 10 min on foot (few services). Free parking for 100 (10 for coaches). The Hiruzen Kogen Centre and the Hiruzen Horse Park on foot to 5 min by car; Yubara Onsen 25 min by car
- Phone
- 0867-66-2155
- Official site
- kaiyukan.jp ↗
- Open in Google Maps
- Google Maps ↗
Essentials
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Why go
- Highland open-air bath facing the Hiruzen peaks
- Cool in summer, snow-viewing in winter
- ¥740; closed Wed
A radium spring at 435 m and a rotenburo facing the three Hiruzen peaks and Mt Daisen
Hiruzen Yatsuka Onsen Kaiyukan is a highland day-use hot spring on the Hiruzen plateau at about 435 metres in Maniwa, Okayama, ringed like a screen by the three Hiruzen peaks and Mt Daisen. The plateau is a semi-highland known for pasture and cycling in summer, foliage in autumn and skiing in winter, and this onsen sits right beside the Kogen Centre, the cycle sports centre and the cycling paths — the perfect place for 'a bath after a day on Hiruzen'. The water is a simple weakly radioactive cold-mineral spring containing radon, colourless and light, known to help gout, arteriosclerosis, high blood pressure and chronic skin disease, and devotees of radium springs come out of their way for it. The bathhouse has a great bath, a rotenburo, sauna and plunge; from the rotenburo the ridges of the three peaks and Daisen are visible, and in winter bathing amid snow mountains and falling snow is its finest moment (hours shorten to 21:00 from December to March). Admission is a modest ¥740 for adults and ¥420 for children, with resident discounts for Maniwa and member discounts for JAF and Montbell (¥600), so travellers should show a membership card or an online discount screen. Open 10:00 to 22:00 (last entry 30 minutes before closing), closed Wednesdays (next day if a holiday), and cash only. Twenty minutes from Hiruzen IC on the Yonago Expressway, 1 h 40 min from Okayama and an hour from Yonago and Daisen, it sits mid-way through a Chugoku journey and pairs well with Yubara Onsen (25 minutes by car, famous for its 'sunayu' sand-bed rotenburo) as a 'two onsen of northern Okayama' course.
A soak after a plateau walk or a ride, and the winter ski flow
Enter from the car park (100 spaces) and pay ¥740 in cash at reception (¥600 with a member discount or an online discount screen shown; ID checked). Towels are sold or rented, shampoo is provided, and you use a locker. The bathhouse is a modest great bath (main tub and bubble bath), a rotenburo through the door, sauna and plunge — a fitting highland arrangement — and from the rotenburo the ridges of the three Hiruzen peaks lie straight ahead with the white summit of Daisen beyond. The water is colourless, odourless and light at a comfortable 40–41°C, with the 'plain look' typical of a radon spring, so the proper way to use it is cure-style bathing — long soaks of 20–30 minutes, two or three times, absorbing radon by breathing. Pairing it with plateau activities is the classic: a walk on the Kogen Centre trails (40 minutes to an hour round trip), cycling the plateau loop (about 20 km, with rental), horseback riding at the Hiruzen Horse Park, or soft-serve of Hiruzen Jersey milk at the farm, then a bath, and the muscle fatigue visibly lifts. In winter (December–March) the peak experience is skiing or cross-country at the Hiruzen Kogen ski area and then the snow-mountain rotenburo; hours shorten to 21:00 then, so come early. There is no restaurant, so eat at the plateau's gelato or soba shops or toward Yubara Onsen, and be sure to bring cash. Remember the Wednesday closure and the infrequent buses (60 minutes from Chugoku-Katsuyama Station); on foliage-season weekends (late October to early November) the car park fills fast.
Practical details and a northern Okayama route
Hours are 10:00–22:00 (until 21:00 from December to March; last entry 30 minutes before closing), closed Wednesdays (next day if a holiday); adults ¥740, children ¥420 (preschool free; member or online discount ¥600), cash only, free parking for 100. Access is 20 minutes from Hiruzen IC, 1 h 40 min from Okayama, or 60 minutes by bus plus a 10-minute walk from JR Chugoku-Katsuyama Station. Suggested routes: (1) a Hiruzen day — plateau walks and cycling with rental bikes in the morning, Hiruzen soba and jingisukan (lamb) for lunch, Jersey soft-serve at the farm, Kaiyukan in the afternoon, a night in Kurashiki or Okayama; (2) two onsen — Yubara Onsen in the morning (the free communal 'sunayu' sand-bed rotenburo), then Kaiyukan (radon) for a water comparison, a night at Yubara or in Maniwa; (3) winter skiing — half a day at the Hiruzen Kogen ski area, Kaiyukan (until 21:00), a stay near the onsen; (4) with Mt Daisen — Daisenji temple and the pastures (an hour by car), Kaiyukan, a night in Yonago; (5) autumn — climbing the three Hiruzen peaks (Kami-Hiruzen is a 5–6 hour round trip, for the intermediate and above), then a bath on the way down. Notes: cash only; closed Wednesdays; no restaurant; shorter winter hours (21:00) and icy roads (winter tyres); few buses; crowded parking on foliage and ski season weekends. Kaiyukan's strengths are its highland setting, radium water and low prices rather than the character of the spring, and it is the best onsen with which to close a day in the mountains of northern Okayama.
Before you go
- No official tattoo policy is published — ask at reception.
- Payment is usually by ticket machine in cash — bring coins.
- Last entry is 30–60 minutes before closing.
Features
Mood & scenery
Sauna & wellness
Price
Amenities
✔ Verified operating: 2026-09 Operating status and rates cross-checked against the official site and onsen guides (full source notes in Japanese on the JA page)
Prices and hours change. Check official sources before visiting.
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