High-alkaline pH 9.8 beautifying water and a spring-fed cold plunge bath
Yamanashi Kosuge Village
Kosuge no Yu, located at the headwaters of the Tama River in Kosuge Village, is a municipally operated day-use onsen surrounded by great nature. Its very high alkaline spring water with pH 9.84 is renowned as a "beauty bath" that leaves skin silky smooth. You can enjoy a variety of baths including a large communal bath, Goemon-style tubs, and open-air rock baths. The sauna room is a carefully designed space using locally sourced schist and herbs, and after the sauna you can experience an exceptional cooldown in the rare spring-fed cold plunge bath that uses the source water directly, producing a clinging, luxurious sensation on the skin.
Typeindoor
A mild simple hot spring with very high alkalinity at pH 9.84. It has beautifying effects that make the skin smooth. You can enjoy it across nine types of baths, including the large communal bath, open-air bath, reclining bath, waterfall bath, and special event baths.
Sauna TypeDry Sauna
Stove Typefar_infrared
Capacity5people
A sauna that uses locally sourced schist under the mats and on the stones. It is set at approximately 90°C to 100°C, and the far-infrared effect promotes thorough sweating. Potpourri of locally grown herbs is placed inside, filling the space with a pleasant aroma.
Water Qualitynatural
Capacity1people
This rare cold plunge bath uses Kosuge no Yu's source water as-is, at about 27°C. Provided in jar baths and Goemon-style tubs, the water temperature varies by season (around 10°C in winter and in the 20s°C in summer). Because the water is strongly alkaline at pH 9.8, the cold plunge bath produces a luxurious, slippery feel on the skin.
Closed Days: Tuesday
3445 Kosuge-mura, Kitatsuru-gun, Yamanashi 409-0211, Japan
Gender Access
Gender Separated
Curated by an expert who visits onsen and sauna facilities every day and has explored 300+ locations — only facilities confirmed to be truly exceptional are featured.
Learn more
High-alkaline pH 9.8 beautifying water and a spring-fed cold plunge bath
Yamanashi Kosuge Village
Kosuge no Yu, located at the headwaters of the Tama River in Kosuge Village, is a municipally operated day-use onsen surrounded by great nature. Its very high alkaline spring water with pH 9.84 is renowned as a "beauty bath" that leaves skin silky smooth. You can enjoy a variety of baths including a large communal bath, Goemon-style tubs, and open-air rock baths. The sauna room is a carefully designed space using locally sourced schist and herbs, and after the sauna you can experience an exceptional cooldown in the rare spring-fed cold plunge bath that uses the source water directly, producing a clinging, luxurious sensation on the skin.
Typeindoor
A mild simple hot spring with very high alkalinity at pH 9.84. It has beautifying effects that make the skin smooth. You can enjoy it across nine types of baths, including the large communal bath, open-air bath, reclining bath, waterfall bath, and special event baths.
Sauna TypeDry Sauna
Stove Typefar_infrared
Capacity5people
A sauna that uses locally sourced schist under the mats and on the stones. It is set at approximately 90°C to 100°C, and the far-infrared effect promotes thorough sweating. Potpourri of locally grown herbs is placed inside, filling the space with a pleasant aroma.
Water Qualitynatural
Capacity1people
This rare cold plunge bath uses Kosuge no Yu's source water as-is, at about 27°C. Provided in jar baths and Goemon-style tubs, the water temperature varies by season (around 10°C in winter and in the 20s°C in summer). Because the water is strongly alkaline at pH 9.8, the cold plunge bath produces a luxurious, slippery feel on the skin.
Closed Days: Tuesday
3445 Kosuge-mura, Kitatsuru-gun, Yamanashi 409-0211, Japan
Gender Access
Gender Separated
Curated by an expert who visits onsen and sauna facilities every day and has explored 300+ locations — only facilities confirmed to be truly exceptional are featured.
Learn more