Osaka Ibaraki City
A full-scale bathing facility with heat-wave löyly, an ice-cold cold plunge bath, and free-flowing source hot spring water
Saito Natural Hot Spring Sumire no Yu is a super sento in Ibaraki, Osaka. Its authentic sauna, featuring heat-wave service by a sauna master and frequent automatic löyly, pairs with a cold plunge bath lined with binchotan charcoal to deliver an intense hot-and-cold alternating bath experience. The light brown simple hot spring that gushes from 1000 m underground also has a free-flowing source bath, and its soft texture keeps you warm and cozy long after you get out.
A mildly alkaline simple hot spring that springs from 1000 meters underground. The light brown water is its hallmark, and the source bath lets you enjoy fresh water flowing continuously. With its soft texture, it warms the body from deep within.
A full-scale sauna kept at a consistently high humidity by automatic löyly that runs frequently. Heat-wave service by a sauna master is also offered, allowing you to sweat profusely at once in pleasantly intense heat that seems to pierce the body.
A low-temperature steam bath filled with the soothing aroma of kampo herbal medicine. Gentle steam wraps the body softly, providing a relaxing sweating experience without any breathlessness while moisturizing the skin.
A cold plunge bath lined with binchotan charcoal. Its defining feature is an intense, stabbing coldness that instantly cools down a body heated to the limit in the sauna, delivering the ultimate toning effect.
Irregular Holidays
Visited by the Editor-in-Chief
The Editor-in-Chief visited in person in May 2026
The Finest Free-Flowing Natural Hot Spring
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Osaka
One of Japan's top saunas — Osaka's most powerful sauna
Osaka
A collection of world baths and Japan's largest 140-person sauna theater
Osaka
A lush premium spa featuring a natural hot spring drawn directly from the source and three types of sauna
JAPAN'S FINEST ONSEN & SAUNA
The Finest Onsen & Sauna in Japan
57 SELECTIONS
Most of what we surveyed never even made it onto this site. This book is a further cut from what did. Our editor bathed in every onsen and sauna in it, and wrote only what they confirmed on the ground.
