Naruko's natural hot spring, loved since the hotel was founded in 1873, flows from three private natural springs. The spring quality is a sodium-sulfate, chloride, bicarbonate hot spring containing sulfur, with a weakly alkaline pH of 8.7. Depending on natural conditions such as temperature, humidity, and wind, the mysterious cloudy water changes color in a variety of ways, including milky white, emerald green, and olive green, and can be enjoyed luxuriously as free-flowing spring water straight from the source. Guests can enjoy bathing around a variety of baths, including a large bath of one of the biggest sizes in Naruko, cypress baths, an open-air Takano-maki cask bath, and a sitting bath.

The hot spring private large bath "Mokko no Yu" offers such an overwhelming amount of space that it hardly feels like a private bath at all. Fresh hot spring water gushing naturally from the hotel’s three private springs is poured in generously, letting you enjoy silky water with excellent skin-beautifying effects in complete privacy. While soaking in the spacious tub, filled with the pleasant scent of sulfur, families and groups can relax without worrying about others and enjoy an exceptional bathing experience that lets them feel the breath of the earth to the fullest.