"Hirayu no Yu" adjacent to the Hirayu Folk Museum is a day-trip hot spring facility exclusively featuring an outdoor bath, which opened in 1975 (Showa 50). Located in the center of Hirayu Onsen, Okuhida Onsen-go, Takayama City, Gifu Prefecture, next to Hirayu Shrine, it is situated on the grounds of the Hirayu Folk Museum where gassho-style traditional houses stand.

The main characteristic of the hot spring is its completely free-flowing (100% natural spring water) tea-brown to yellowish-brown colored water. The high-temperature water containing iron and having a faint sulfur smell flows abundantly into the outdoor bath surrounded by trees. Locally, it is affectionately called "nukutomari-yu" (meaning "warming water"), and it is reputed to warm you to the core. The beautiful tea-brown color has a transparency of about 40 centimeters, and its rustic atmosphere is highly valued even by hot spring enthusiasts.

The facility is extremely simple, consisting only of a changing room and an outdoor bath. There are no showers or washing areas, and you cannot wash your body or hair, but this actually enhances the atmosphere of a remote hot spring. The outdoor bath is in a naturally rich environment surrounded by trees, where visitors can enjoy bathing while viewing beautiful nature throughout the four seasons: fresh greenery, autumn leaves, and snowy landscapes. The outdoor bath where you can listen to the murmuring of a stream has the true character of a hidden hot spring in the mountains.

The bathing fee is based on a "voluntary donation" system, with about 300 yen requested as a cleaning cooperation fee. This conscientious pricing system reflects its character as a public bath rooted in the local community. After bathing, visitors can rest for free in the rest area inside the adjacent gassho-style building, relaxing while surrounded by the aroma of the irori (hearth).

The Hirayu Folk Museum houses two precious old private houses: the gassho-style "Former Takakuwa House" relocated from Toga Village, Toyama Prefecture over 40 years ago, and the "Former Toyosaka House" (built in the mid-Edo period, irimoya-style) relocated from the Kurabashira district, designated as a cultural property of Takayama City. Inside, there is an irori with a fire constantly burning, and old farming tools, folk implements, and Buddhist statues carved by Enku are displayed. Additionally, the grounds include a memorial hall for Shinohara Buzen, who came to Hirayu during the Taisho period and was called the "Father of Hida Social Education," as well as Hirayu Shrine, Yakushido (Healing Buddha Hall), and terraced rice field ruins, making it a hidden spot where you can experience Hirayu's history and culture all at once.

The restaurant "Rokuji" is also on the premises, where you can enjoy local delicacies such as mushroom soba and udon, mitarashi dango (rice dumplings), and Hida beef skewers. Additionally, a large barrel-shaped free foot bath is installed at the entrance, providing an environment where visitors can easily experience the hot spring.