A precious natural hot spring with an astonishingly high salt and iron content, said to be one of the finest in Japan, formed by ancient seawater trapped underground and known as "fossil seawater" (a blend of the fourth and fifth sources, as well as the third source). It is poured as 100% luxurious free-flowing natural spring water, with outstanding warming and moisturizing effects that prevent you from losing heat after bathing, keeping your body warm and comfortably hot for a long time.

In this open-air area surrounded by lush greenery, you can enjoy a rock bath fed by the property's own second source, a sodium-chloride and sodium bicarbonate cold mineral spring. The water has a gentle feel on the skin, making it ideal for long, leisurely soaks. You can experience a luxurious, soothing bath while feeling the pleasant mountain breeze of Mount Koya across your entire body.