A spacious far-infrared dry sauna filled with the warmth of wood, located in the large public bath Onioshionsen. The room is set to a high temperature that lets you feel the heat firmly, and the far-infrared stove helps promote deep sweating efficiently from head to toe. A moderate level of humidity is also maintained, making it a very comfortable and clean sauna room where you can slowly warm your body to the core and refresh yourself against the backdrop of the cool highland climate.

A refreshing cold plunge bath placed right in front of the sauna room and proudly known for its crisp, invigorating feel. It draws pure water from Kita-Karuizawa and quickly cools your heated body after the sauna for a refreshing cooldown. With less of the distinctive harshness of chlorine and a smooth water quality, it feels pleasant on the skin. This clean cold plunge bath is indispensable for contrast bathing, linking the sauna to outdoor air baths in the open-air area or relaxation space within the large public bath.

A rare lukewarm bath set near the sensory-neutral range, placed right next to the cold plunge bath. Kept at a comfortable temperature slightly below body temperature, it allows even those who do not like water that feels too cold to gently settle the heartbeat without putting strain on the body after the cold plunge bath. Enjoy contrast bathing between hot and cold baths, or the ultimate floating totonou experience after the sauna, with this superb facility.