Aragi Kosen
- Location
- Ogano, Saitama, Japan
- Water type
- iron-rich
- Temperature
- 25 °C
- pH
- 6.3
Water profile
Stimulating — wakes the body and boosts circulation.
Rich in active gases or metals — a strong mineral character.
Soft water — natural, classic buoyancy.
Aragi Kosen in Saitama Prefecture is a technically cold spring — carrying the kosen designation indicating a natural emergence temperature below the 25°C threshold required for hot spring classification in Japan — yet its extraordinary triple mineral profile of bicarbonate, ferruginous, and carbonated chemistry makes it one of the most mineralogically complex natural spring sources in the Kanto region, offering therapeutic qualities that rival many of Japan's heated onsen. The rare coexistence of bicarbonate alkalinity, iron-rich ferruginous content, and dissolved carbon dioxide effervescence in a single cold spring source reflects the exceptional geological complexity of the volcanic and sedimentary formations underlying eastern Saitama, where deep mineral-bearing water surfaces with a chemical richness that temperature alone cannot define. Aragi Kosen invites visitors to discover that Japan's natural spring heritage encompasses not only the volcanic heat of famous mountain onsen but also the mineral wealth of cold springs whose therapeutic chemical complexity is as remarkable as anything produced by the volcanic geothermal systems of Hokkaido or Kyushu.