Yunotsu Onsen is one of the San'in region's most historic hot springs, located in the town of Yunotsu in Oda City, Shimane Prefecture, with a history spanning approximately 1,300 years. According to legend, a traveling monk discovered the spring after observing a wounded badger healing its injuries by bathing in the hot water. During the Sengoku and Edo periods, Yunotsu flourished as the shipping port for silver from the Iwami Ginzan silver mine, and in 2007, it was registered as a component of the UNESCO World Heritage Site "Iwami Ginzan Silver Mine and its Cultural Landscape" — making it the first hot spring town in Japan to receive World Heritage designation.

Yakushiyu is a public bathhouse whose source spring emerged following the Hamada Earthquake of 1872, earning it the alternate name "Shinyu" (Earthquake Spring). The water is classified as a sodium chloride spring (hypotonic, neutral, high-temperature) with a pH of 6.3 and a source temperature of 44.4 degrees Celsius. The mineral-rich water contains 1,950mg of sodium ions, 450mg of calcium ions, 976mg of bicarbonate ions, and 537mg of free carbon dioxide per kilogram. Yakushiyu received the highest possible rating of 5 in all six categories from the Japan Hot Spring Association's natural hot spring evaluation — the only facility in the San'in region to achieve this distinction. The water flows directly from the source at 100% concentration without dilution or recirculation, appearing colorless and transparent when it emerges but turning a light brownish hue in the bathtub.

The current Yakushiyu complex consists of the former building, a Western-style wooden structure built in 1919 during the Taisho era (now repurposed as the Shinyu Gallery and Shinyu Cafe Naikuranosuke), and the adjacent new bathhouse building. Admission is 450 yen for adults and 200 yen for children. Operating hours are 6:00 to 21:00 on weekends and holidays, and 8:00 to 21:00 on weekdays, open year-round. Private baths are also available at 800 yen per adult. Free parking is available for 30 vehicles.