Deyu Onsen Seikokan

Seikokan is a long-established inn in Deyu Onsen, part of the Gozu Onsen resort area at the foot of the Gozu mountain range in Agano City, Niigata Prefecture. Deyu Onsen is said to have been opened about 1,200 years ago by the monk Kobo Daishi, making it the oldest hot spring in Niigata, and Seikokan itself has more than 300 years of history. Built by a shrine carpenter, the three-story wooden building is a Registered Tangible Cultural Property of Japan, and the craftsmanship of the early Showa era lives on throughout, from the thick single-slab keyaki alcove to the elaborately designed study rooms.

The inn's private source is a simple weak radioactive spring, emerging lukewarm at around 33 degrees Celsius. Containing trace amounts of radium, it is said to ease neuralgia and muscle pain and to benefit the skin. The self-flowing source is used at 100 percent free-flow, with no circulation equipment and no chlorine disinfection; it is only gently heated to a comfortable temperature. The water is colorless, transparent, and soft to the touch.

Bathing is provided in two indoor baths, separated by gender: a large stone-and-tile bath and an unpainted all-cypress bath. There is no open-air bath. All 11 guest rooms have distinct designs, and the entire building is non-smoking with WiFi. Day-trip bathing is not accepted, so the baths are for overnight guests only. Rates start at 15,000 yen (16,650 yen including tax) per night with two meals. Check-in is 15:00 and check-out 10:00.