Muro no Yu is a public bathhouse representing Shirahama Onsen, one of Japan's Three Ancient Hot Springs, located in the Yuzaki hot spring district of Shirahama Town, Nishimuro District, Wakayama Prefecture. Shirahama Onsen has a history spanning over 1,400 years, known in ancient times as Muro no Onyu and Ki no Onyu. It is recorded in the Nihon Shoki and Man'yoshu, and was visited by emperors including Saimei, Jito, and Monmu for therapeutic bathing.

The defining feature of Muro no Yu is the opportunity to enjoy two distinct spring sources in a single visit. The Mabuyu source is a sulfur-containing sodium chloride strong salt spring at 74.0 degrees Celsius with a flow rate of 190 liters per minute and a pH of 7.3. The Miyuki source is a sodium chloride spring at 78.0 degrees Celsius with a pH of 7.9. Each source feeds separate bathing pools, allowing visitors to compare the different mineral waters.

The facility features indoor baths only, with separate bathing areas for men and women, each containing two pools. Admission is 420 yen for adults, 140 yen for children aged 6 to 11, and 80 yen for children aged 3 to 5. Operating hours are 9:00 to 11:00 and 14:00 to 21:30, with last entry at 21:00. The bathhouse is closed every Tuesday. Free parking is available for 5 to 7 vehicles.