Atsugi Onsen

Atsugi, Kanagawa, Japan

Location: Atsugi, 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

Atsugi Onsen invites bathers to enjoy siliceous mineral thermal waters in the city of Atsugi, an inland Kanagawa city that promotes itself as an onsen destination—marketing its dark kurotsuyu (black water) onsen drawn from deep geological layers where ancient organic matter imparts a tea-colored mineral richness prized in Japanese bathing culture for skin-conditioning and warming properties. The city of Atsugi, home to major corporate headquarters, sits in the Sagami River valley between Yokohama and the Tanzawa-Oyama State Quasi-National Park, offering both industrial economic dynamism and mountain recreational access within the same commuter-friendly location. The Tanzawa range's mountain streams, the Sagami River's traditional runs, and the healing dark mineral waters of Atsugi's distinctive petroleum-impregnated onsen give this Kanagawa city an unexpected hot spring identity among Japan's metropolitan suburban centers.

Insider tip — Atsugi Onsen draws dark sodium-chloride mineral water from deep underground formations beneath the Sagami River valley, a geothermal profile shared by many famous Kanto baths. The city of Atsugi sits between the coastal Kanagawa plain and the Tanzawa mountain range, offering both urban convenience and proximity to nature. The sodium-rich kuronyu water turns the bath dark amber-brown and leaves skin notably soft after soaking. Atsugi's onsen facilities often include outdoor露天 (rotemburo) baths with views of the surrounding hills.

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