Ayase Onsen

Ayase, Kanagawa, Japan

Location: Ayase, Kanagawa, Japan
Water type: sodium chloride
Temperature: 41 °C
pH: 7.3

Water profile

Thermicity

Sedative

41 °C

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

Ayase Onsen is a community thermal facility in the city of Ayase, a small inland Kanagawa city in the Sagami plain between Atsugi and Ebina on the railway corridor connecting central Kanagawa with the Tokyo metropolitan network. The siliceous mineral waters provide warm bathing for a compact residential community whose city developed rapidly as a postwar industrial satellite of Yokohama and Yokosuka, home to light manufacturing and logistics facilities serving the broader Kanagawa economy. The Tanzawa mountain skyline visible from Ayase's streets and the agricultural remnants of the once-rural Sagami plain—traditional vegetable fields and lotus ponds—give this neighborhood onsen a pleasant domestic counterpoint to the industrial modernity of its urban surroundings.

Insider tip — Ayase Onsen taps the deep sodium-chloride aquifer beneath the Sagami Plain in northern Kanagawa, yielding the characteristic dark natto-colored thermal water beloved across the Kanto region. The city of Ayase borders Sagamihara and Ebina, sitting within a network of commuter railways connecting to Yokohama and Tokyo. These urban onsen facilities serve as neighborhood wellness anchors, with regulars visiting several times per week for the warming mineral soak. The high chloride content helps retain body heat well after leaving the bath.

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