Shiobara Motoyu Onsen Oidekan

Oidekan is a single-inn hot spring standing in the Motoyu district at the very back of the Shiobara Onsen area in Nasushiobara City, Tochigi Prefecture. Motoyu is regarded as the birthplace of Shiobara Onsen, an ancient spring said to have been opened in 1142 during the Heian period, set along a tributary of the Hoki River at an elevation of about 700 meters. Oidekan is a member of the Association to Protect Japan's Secret Hot Springs and sits in a quiet setting ringed by deep mountains.

The water is a sulfur-bearing sodium chloride-bicarbonate spring of the hydrogen sulfide type, with a source temperature of roughly 50 to 53 degrees Celsius and a near-neutral pH of about 7.1. The inn draws on eight of its own spring sources. The most famous is Sumi-no-yu, an iron-rich bath so dark it looks as though ink has been poured into it, said to be the only one of its kind in Japan. Another signature bath is Goshiki-no-yu, whose color shifts with the weather and temperature. All baths are one hundred percent free-flowing spring water, and drinking the water is also permitted.

The inn offers eight tubs in total, including Sumi-no-yu (indoor, mixed bathing, women-only from 14:00 to 15:00), Gosho-no-yu (open-air, mixed bathing), a private indoor bath, and women-only indoor and open-air baths. Day-use bathing costs 700 yen for adults and 400 yen for children, with reception from 10:00 to 14:00 and use until 16:00. Overnight stays start at 14,000 yen with two meals, across 26 rooms. Telephone: 0287-32-2438.