Hirauchi Kaichu Onsen
Hirauchi Kaichu Onsen is an undersea hot spring with a magnificent view of Yakushima’s southern coast. According to oral legend, about four hundred years ago locals stumbled upon steam rising from the rocks on the beach. They decided to create small pools for bathing by piling up rocks, and those pools form the current hot spring.
Its beach location means Hirauchi Kaichu Onsen can be accessed only during low tide. It is open twice each day, for two hours before and two hours after low tide. There is a timetable hanging on a nearby building that details the day’s access times.
Hirauchi Kaichu Onsen features three baths with space for about fifteen people each. All baths are gender-mixed, and visitors are allowed to keep a towel inside the water to preserve modesty. The temperature of the water is between 38 to 40°C and varies according to the volume of tides. Although free to enter, a donation of 200 yen is requested to help clean and maintain the onsen.