— 100% Source-Flow
Completely natural spring water flows continuously through the baths and overflows the rim — never recirculated.
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— — 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.
— 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
— Reservations
Plan your visit.
Day-visit bathing requires no reservation. To stay the night, please book online or call us — our staff will do their best to help in English.