https://www.princehotels.com/en/onsen/manza/
Manza, an alpine hot spring situated at an elevation of 1,800 meters boasting one of the highest sulfur content in Japan, is known as “the closest hot spring to the stars.”
Hot Springs Guide
The Hotel’s open-air hot spring baths (“rotenburo”) include mixed-gender baths. For male guests, we have provided a towel in your room to wear around your waist in consideration toward female guests. For female guests, bath towels suitable for mixed bathing are available on loan from the front desk, or you can purchase a special bathing suit from the shop.