Kyūsuikei Onsen
- Location
- Usa, Oita, Japan
- Water type
- calcium-rich
- Temperature
- 41 °C
- pH
- 7.3
Water profile
Relaxing — deep, immediate muscle release.
Loaded with major ions — the essential minerals (Ca, Mg).
Soft water — natural, classic buoyancy.
Kyusuikei Onsen in Oita Prefecture flows with calcareous thermal waters, a mineral type associated with the calcium carbonate deposits typical of the limestone karst landscapes that characterize parts of Kyushu's mountainous interior, producing water with a distinctive mineral clarity and gentle hardness that sets it apart from the more commonly encountered bicarbonate and sulfurous springs. Oita Prefecture is renowned throughout Japan as one of the country's premier onsen regions — home to Beppu, Yufuin, and a remarkable density of geothermal resources — and Kyusuikei Onsen contributes to this thermal heritage with its distinctive calcareous mineral profile. The spring's unique water chemistry and its position within one of Japan's most thermally rich prefectures make it a destination of particular interest for onsen enthusiasts seeking the full diversity of Kyushu's extraordinary geothermal mineral landscape.