Sainokawara Open-Air Bath is a day-trip hot spring facility in Kusatsu Onsen, a hot spring resort representative of Gunma Prefecture. It is located at the very back of Sainokawara Park, which can be reached on foot from the Yubatake in the center of the hot spring town. The main features of this open-air bath are its spaciousness and its design that is integrated with nature. The open-air bath, which is one of the largest in Japan at about 500 square meters, allows you to enjoy the high-temperature spring water flowing from the Yubatake. In addition, trees and flowers grow around the open-air bath, allowing you to spend a relaxing time while watching the nature of the four seasons.

Sainokawara Open-Air Bath uses the Bandai source and is a highly acidic (acid chloride sulfate spring, pH 1.6-1.7) spring water. The source temperature is high at about 97°C, and although it is adjusted to the appropriate temperature, it is important to note that the area near the source in the bathtub has a strong tingling sensation. The clear water contains about 500mg/kg metasilicic acid and about 15mg/kg free carbon dioxide, and its strong bactericidal power is effective against neuralgia, joint pain, and skin diseases. It is also rich in moisturizing ingredients, and is popular as a skin-beautifying bath that smoothes the skin.

[Mixed Bathing]
At Nishinokawara Open-Air Bath, the men's open-air bath becomes a mixed bath every Friday from 17:30 to 20:00 (last entry 19:30), and couples and families can bathe together. Please be sure to wear a swimsuit or bathing suit during mixed bathing hours. Bathing suits are free to rent for men, and can be rented for women for 400 yen if desired. There are no children's suits, so you must bring your own swimsuit. Women can use the regular women's bath or enter the men's bath directly through a door installed without going through the changing room. Outside of mixed bathing hours, men and women bathe separately.