Rankeiso

A riverside secluded-onsen inn with a registered cultural-property wooden building, salty therapeutic water, free private baths and mountain-village kaiseki of carp and wild vegetables — but the spring is heated and recirculated, and the old wing carries sound

Rankeiso stands alone beside a mountain stream in the hills east of Sanjō; its founder hand-dug the well in the late Taishō era, when the salty water was even sold in Tokyo as medicine. A member of the Japanese Association of Secluded Hot Spring Inns, it has 17 rooms in three buildings, the star being Ryokufūkan, an early-Shōwa wooden inn moved here from Tsubame in 1955 and registered as a national tangible cultural property in 2012. The water is a very salty sodium chloride cold spring (about 15.7 g of minerals per kg) that emerges at 16.5°C, so it's heated and recirculated — the inn's own posting makes that clear, and several guests notice chlorine. Japanese guests still rate it 4.64 across 364 reviews on one major site and 4.7 across 46 on another, with dinner and baths near the top. They love the views of the stream, the two free private baths — Ishi-yu of river stones and the 130cm-deep standing bath Fuka-yu — and the yamazato kaiseki served in private rooms: raw carp with no muddy taste, salt-grilled river fish, whole-stem fern, and a breakfast of rice porridge cooked in spring water. The complaints: noise and (before a late-2025 renovation) stink bugs in Ryokufūkan, shared toilets in most of its rooms, a maze of steps, small outdoor baths, a disinfectant smell, and food some found dated or too salty. Recent guests paid about ¥26,000–32,000 per person with two meals.