Shinzaemon no Yu

Shinzaemon no Yu is a serene day-use onsen nestled in the historic hot spring town of Zao Onsen, Yamagata Prefecture. Renowned for its highly acidic, sulfur-rich waters—among the most potent in Japan—this facility offers a rejuvenating experience amidst the natural beauty of the surrounding mountains.​

The onsen features a variety of baths, including gender-separated indoor and open-air pools, as well as specialized options like the Shiroku no Yu, which is gentler on sensitive skin.

Beyond the baths, Shinzaemon no Yu provides amenities such as a restaurant serving local Yamagata specialties, spacious relaxation rooms, and a souvenir shop. Its convenient location—opposite the Zao Chuo Ropeway—makes it an ideal stop for visitors exploring the area.