Osawa Onsen Notenburo Yamanoie

Osawa Onsen Notenburo Yamanoie is a day-use hot spring centered on open-air baths, set along the Ikashiro River in the mountains of western Izu, in Osawa, Matsuzaki Town, Kamo District, Shizuoka Prefecture. The source is said to have been discovered around 250 years ago in the mid-Edo period, and it has been known since its opening as the beautifying bath. The facility adjoins a self-catering therapeutic lodge, Osawaso Yamanoie, and charms visitors with its rustic mountain-village setting where wild sweetfish swim in the clear stream and fireflies and river frogs thrive.

The spring is a calcium-sodium sulfate spring (hypotonic, weakly alkaline, high-temperature), with a pH of about 8.4 and a source temperature of roughly 46.7 degrees Celsius. The water wells up naturally from the very floor of the rock-hewn bath at about 230 liters per minute, a genuine foot-of-the-bath source that is served entirely free-flowing without any heating or dilution. It is colorless and clear with a soft feel on the skin, and is said to be effective for high blood pressure, neuralgia, and skin conditions.

The bathing area offers gender-separated open-air baths and a private bath available in 50-minute slots. Admission is 600 yen for adults and 300 yen for children, with an extra 300 yen to use both the open-air and private baths. It is open from 9:00 to 21:00 (last entry 20:30) and closes on the second Wednesday of each month. Overnight stays are self-catering from 4,800 yen per night.