Kozushima Onsen Hoyo Center

A day-trip hot spring facility located in Sabisaki, Kozushima Village, Tokyo, on the southwestern coast of Kozushima Island near the center of the Izu archipelago. The predecessor bath, Sabisaki Onsen, opened in 1988, and the facility was rebuilt as the current Kozushima Onsen Hoyo Center in 1994.

The spring water is a sodium chloride strong salt spring with a source temperature of 56.5°C and a neutral pH of 7.37. It flows at an abundant 420 liters per minute and contains 34.76 grams per kilogram of dissolved minerals, a concentration close to seawater. Both the indoor and outdoor baths are supplied directly from the source (kake-nagashi), diluted slightly to adjust the temperature.

The facility features a 275-square-meter open-air bath along with two more outdoor pools -- one overlooking Sawajiri Bay and a roofed observation bath -- all mixed-gender and requiring swimwear, plus gender-separated indoor baths with bubble baths, jet showers, and pressure-jet tubs. Hours are 11:00 to 20:00 (last admission 19:00), closed on Wednesdays except during summer, Golden Week, and New Year. Admission is 800 yen for adults and 400 yen for children.