— 100% Source-Flow
Completely natural spring water flows continuously through the baths and overflows the rim — never recirculated.
Sasanoyu
A secret hot spring at the foot of Mt. Hotaka.
— Pure Hot Spring A — 100% Source-Flow
— Welcome
Sasanoyu is a small, quiet hot spring inn in the mountain village of Katashina, Gunma — the gateway to the Oze marshlands. Our water rises from 1,000 metres underground and flows straight into the baths: no added water, no reheating, no recirculation, no chlorine. In October 2021 it was certified Pure Hot Spring “Class A”, the strictest grade awarded in Japan.
— The Onsen
The hot spring
— 270 ℓ / min
An abundant supply means every bath is constantly refreshed with new water straight from the source.
— Skin-friendly
A clear, alkaline simple spring (pH 8.7) with a soft, silky feel — known locally as a “beauty bath.”
- Spring type
- Alkaline simple spring
- Temperature
- 40–42°C (natural, unheated)
- pH
- 8.7
- Flow
- Approx. 270 ℓ / min, free-flowing
Guests with tattoos are welcome to bathe. Please note that baths are gender-separated and bathing is enjoyed without swimwear, in the traditional Japanese way.
In the colder months the outdoor bath cools down in the winter air and can feel chilly at first. Our water is gently warm, so we recommend a long, slow soak in the indoor bath first, then stepping outside to cool down.
— Pricing & Hours
Day visit
— Stay
Spend the night
Five simple Japanese-style rooms and home-cooked meals made with local highland vegetables, Joshu pork, and Akagi chicken. Two-meal plans are served on Fri–Sun and the day before public holidays; room-only stays are available on weekdays.
— Access
Getting here
— FAQ
FAQ
Common questions about staying and bathing with us
そのほかのご質問は、お電話でお気軽にどうぞ。
0278-58-3630Weekday stays (Mon–Thu) are room-only. Meal plans such as dinner & breakfast are available on Fri, Sat, Sun, public holidays and in high season (Golden Week, Obon, New Year). If you are unsure, please call us at +81 278-58-3630.
Check-in is 15:00–20:00 and check-out is 11:00. Dinner is served from 19:00 and breakfast from 8:00; ask us if you would like another time. Please check in by 20:00. If you cannot avoid arriving later, call us in advance: late check-in costs ¥1,000 per hour after 20:00, and the latest check-in is 22:00, when the baths also close.
Rooms do not have a private bath or toilet — guests use the shared hot spring baths, toilets and washbasins. Hair dryers are in the bath changing rooms. The onsen is open until 22:00 at night; the morning bath is available from 7:00 on Sundays only during the peak seasons (Jul 13 – Sep 30 and Dec 19 – Mar 31); there is no morning bath in the off-season (Apr 1 – Jul 12 and Oct 1 – Dec 18). We drain and clean the baths every day and refill them with fresh spring water, so the water is always clean. Thank you for your understanding.
100% on the day of stay, 50% from 3 days before up to the day before (for meal-inclusive plans), and free if cancelled 4 or more days in advance.
We do our best to accommodate allergies — please let us know when you book. Note that we cannot always guarantee the complete removal of an ingredient.
Yes, Wi-Fi is available. The details are posted on the information board inside the inn.
We recommend booking early. Weekends and peak seasons fill up quickly, so please reserve as far in advance as you can.
No reservation is needed for day-visit bathing — simply come during opening hours.
Towels are available at the front desk: face towel ¥250, bath towel rental ¥400.
Yes. Guests with tattoos are welcome to bathe. We want everyone to feel at ease here.
Yes, even babies can bathe safely in our gentle, Class A certified spring. Children under 3 bathe free of charge.
Yes. We accept major credit cards, e-money, and QR-code payments.
We are sorry, but pets are not permitted. Only guide dogs and hearing-assistance dogs are allowed.
そのほかのご質問は、お電話でお気軽にどうぞ。
0278-58-3630— Reservations
Plan your visit.
Day-visit bathing requires no reservation. To stay the night, booking online costs less than calling. You can also call us — our staff will do their best to help in English.