A day-use hot spring facility where you can enjoy Happu Onsen, a rare natural hot spring in the Karuizawa area. The bicarbonate spring, regarded as one of the three 'beautifying' spring types, is gentle on the body and is said to be effective for cuts and improving skin. Surrounded by warm dappled sunlight and star-filled skies, you can fully enjoy the sauna, cold plunge bath, open-air baths, and more.