Kuroyu Onsen

Kuroyu Onsen stands as one of the most historic and secluded hot spring retreats in Japan's Nyuto Onsen area. First discovered around 1674, this remote mountain onsen boasts over 350 years of history dating back to the Edo period. Located in Towada-Hachimantai National Park in Akita Prefecture, Kuroyu Onsen was discovered in the 1670s during the Edo period and served as the official hot spring of the Akita Satake clan. The name translates to "black hot spring," though some suggest it derives from a mispronunciation of the local dialect word "kuruyu," meaning "to come."

The onsen occupies a pristine setting deep within virgin beech forests at the source of the Sendatsu River. Waters are sourced by two abundant hot springs, making it the most water-rich onsen in Nyuto Onsen Village. The mineral-rich waters display a cloudy bluish appearance due to high sulfur content and are believed to help with hypertension, arteriosclerosis, circulatory issues, and diabetes. The unique sulfur concentration creates one of Kuroyu's signature attractions: black hard-boiled eggs prepared by submerging fresh eggs in nets at the hot spring source, where chemical reactions turn the shells black while the interior remains white.

Visitors can choose from several bathing options, including a rare mixed-gender open-air bath surrounded by forest, separate men's and women's facilities with both indoor and outdoor baths, and natural massage areas where spring water cascades from spouts. The hot spring overlooks a stream where hot spring water gushes from its underground source, creating an atmosphere of steaming vapors and murmuring water. The traditional thatched-roof buildings and wooden structures maintain an authentic therapeutic retreat atmosphere that has welcomed guests for centuries.

Accommodation ranges from traditional tatami rooms to Western-style options, with some rooms featuring private onsen baths. The traditional inn serves seasonal dishes made with the rich produce of the mountains. Self-service camping-style units with in-room firepits are available for those seeking a more rustic experience. Day visit admission is 600 yen for adults (junior high school students and older), 300 yen for elementary students, and free for preschool-aged children. The Yumeguri-cho pass at 1,800 yen includes admission to all seven hot springs in the Nyuto Onsen area plus bus transportation between inns, making it ideal for onsen-hopping enthusiasts.

Kuroyu Onsen is accessible from Tazawako Station on the JR Akita Shinkansen, approximately three hours from Tokyo Station. From Tazawako Station, take the Nyuto Onsen bus for about 50 minutes to the Kyukamura-mae stop, then walk 25 minutes to reach the onsen. Free pick-up service is available from the final bus stop, Ganiba Onsen, for overnight guests with advance reservation. For those traveling by air, Akita Airport is the nearest option, located 14 kilometers southeast of Akita Station. Visitors with rental cars will find parking available, though luggage must be carried down a semi-paved walkway from the parking area to the onsen buildings.