Kakuma Onsen (Nagano)

Nakano, Nagano, Japan

Location: Nakano, Nagano, Japan
Water type: bicarbonate, carbonated
Temperature: 40 °C
pH: 6.3

Water profile

Thermicity

Sedative

40 °C

LowHigh

Relaxing — deep, immediate muscle release.

Mineralisation

Restorative

LowHigh

Loaded with major ions — the essential minerals (Ca, Mg).

Buoyancy

High buoyancy

LowHigh

Mineralised water — eases movement and joints.

CO2BicarbonatesMagnésium

Kakuma Onsen in the Sanada-machi area of Ueda City, Nagano Prefecture, is celebrated as a hidden spring of the Sanada clan—the legendary samurai family whose military genius, fierce independence, and ultimate tragedy at the Battle of Osaka (1615) made them the subject of enduring Japanese historical romance, and who reportedly concealed this spring for the private restorative use of their warriors across the mountain campaigns of the Warring States era. The bicarbonate and carbonated waters offer an effervescent, skin-stimulating soak that Sanada warriors would have valued for recovering from battlefield fatigue, and the hidden valley setting now accessible to all preserves the atmosphere of strategic secrecy that defined the clan's approach to every resource. Note: Nagano Prefecture has two springs named Kakuma Onsen, the other being in Yamanouchi-machi as part of the Yudanaka Shibu Onsenkyo cluster.

Insider tip — Kakuma Onsen in Nagano's Nakano district taps a bicarbonate-carbonated spring that produces pleasantly effervescent baths prized for improving circulation and digestion. The Nagano basin surrounding the spa is celebrated for its apple orchards, which turn the valley floor pink each spring. Local inns serve regional dishes including oyaki dumplings stuffed with mountain vegetables. The carbonated water here is mild enough to drink straight from the source, a rare treat for visitors.

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