Kamimasuda Onsen; Toride no Yu
Annaka, Gunma, Japan
- Location
- Annaka, Gunma, Japan
- Water type
- sodium chloride, thermal
- Temperature
- 40 °C
- pH
- 7.3
Water profile
Thermicity
Sedative
LowHigh
Relaxing — deep, immediate muscle release.
Mineralisation
Restorative
LowHigh
Loaded with major ions — the essential minerals (Ca, Mg).
Buoyancy
Effortless float
LowHigh
Dense, salty water — you float without effort.
SodiumChloruresBrome
Kamimasuda Onsen, also known as Toride no Yu, is located in Annaka, Gunma prefecture. Its sodium-chloride water reaches around 40°C. The complex includes an indoor bath, an outdoor bath and a sauna, set in a rural area typical of central Japan.
Insider tip — Annaka stands at the base of the historic Usui Pass — the most dramatic mountain crossing of the old Nakasendo Highway between Kanto and Nagano, where the road gains 450 meters in altitude through hairpin switchbacks. The 'Toride' (fortress) in the onsen's name recalls the Matsuida mountain fortress that controlled this strategic pass. Today, Usui Pass is Japan's most celebrated vintage driving road — the hairpin curves immortalized in the Initial D manga about drift racing. Annaka's springs provide warming sodium-chloride waters in a city that has always guarded the gate between two worlds.
Nearby
Frequently asked questions
How hot is the water?
The water runs quite hot here, around 40 °C — a sedative water that brings immediate muscle release.
What type of water is found here?
This spot features sodium chloride & thermal water.
What is the best season to visit?
The most favourable period for this spot is: Toute l'année.