Yudomari Hot Spring is a seaside outdoor hot spring located in the Yudomari district of Yakushima Town, Kumage County, Kagoshima Prefecture. Situated along the southern coast of Yakushima, this precious hot spring resource has been beloved by locals for over 400 years on this island renowned as a UNESCO World Natural Heritage Site. Historical records show that local people were already bathing here during the Meiji era, making it an important site that tells the story of Yakushima's hot spring culture.

The main feature of this hot spring is its natural spring water that emerges on the beach, offering an open-air bathing experience with spectacular views of the bright blue sea. The concrete-enclosed baths are separated into male and female sections by bamboo screens. While bathing suits and underwear are prohibited, bathing with a bath towel wrapped around the body is permitted. There are no changing rooms, so visitors must change in the natural environment.

The scenery features the beautiful blue waters of the East China Sea stretching out before you, surrounded by Yakushima's rich natural environment. The sunset hours are particularly spectacular, offering an unforgettable experience of bathing while watching the sun set over the horizon. Night bathing under a star-filled sky is also possible, and locals have a tradition of conversing in the hot spring while gazing at the stars.

Nearby is the famous Hirauchi Kaichu Onsen, an ocean hot spring accessible only during low tide, but Yudomari Onsen is unaffected by tidal changes, making it accessible 24 hours a day. This makes it more accessible to tourists than Hirauchi Kaichu Onsen and a place where visitors can leisurely enjoy the hot spring experience.

In terms of popularity, it's known among hot spring enthusiasts as a hidden gem of Yakushima, attracting many tourists for post-trekking recovery and to fully appreciate the island's nature. However, it's less crowded than Hirauchi Kaichu Onsen and remains a relatively peaceful spot for bathing.