Tsurunoyu Onsen (Ogouchiso)

Tsurunoyu Onsen is a hot spring available at a single lakeside inn, Ogouchiso, in Hara, Okutama Town, Nishitama District, Tokyo, within Chichibu Tama Kai National Park on the shore of Lake Okutama. Tradition holds that the spring was first opened during the Enbun era of the Nanboku-cho period (1356-1361), and it takes its name from a legend of an injured crane (tsuru) healing its wounds in the water. Originally there were three separate sources, known as the Deer Spring, Insect Spring, and Crane Spring, but the entire spring area was submerged when the Ogouchi Dam was built to create Lake Okutama. Long called a 'phantom hot spring,' it was revived in 1991 when the submerged pumps were repaired, combining the three sources into one and delivering the water to nearby inns by tanker truck.

The water is classified as an alkaline simple sulfur spring with a notably high pH of 9.68 (measured July 1, 1991). The source emerges at a low temperature of 30.2 degrees Celsius and carries a faint sulfurous, egg-like scent, with a clear, colorless appearance. Because the source temperature is too low for direct bathing, the water is heated before being supplied to the baths.

Ogouchiso is a small two-story inn built entirely of cypress, with five guest rooms and a maximum capacity of eight guests, operating strictly by reservation. It offers two indoor baths, a cypress-wood bath on the second floor and a chrysanthemum-stone bath on the first floor, which alternate between men and women morning and evening. Bathing hours run from 15:00 to 23:00 and again from 6:00 to 9:00. A one-night stay with two meals costs 12,250 yen for adults (bathing tax included) and 8,620 yen for elementary school children, with cash-only payment accepted. The inn closes for winter every year from December 20 through the end of February.