Sukayu Onsen is one of Japan's most renowned hidden hot springs, located at an elevation of approximately 925 meters on the western slope of Mount Odake, the main peak of the Hakkoda Mountains in southern Aomori City, Aomori Prefecture. In 1954, it was designated as Japan's first National Health Resort Hot Spring alongside Shima Onsen and Nikko Yumoto Onsen, boasting a prestigious history of approximately 340 years.

The hot spring's discovery dates back to 1684 during the early Edo period. According to legend, a hunter named Chonai Saemon Shiro from Yokouchi Village was tracking a wounded deer in the mountains. Three days later, when he found the deer, he was amazed to see it swiftly climbing rocky cliffs despite its injuries. This led him to discover the healing hot spring. Initially called "Shika-no-Yu" (Deer Hot Spring), the name evolved into "Sukayu."

The signature feature is the "Hiba Sennin-buro" (Hiba Thousand-Person Bath), a magnificent communal bathhouse made entirely of Hiba cypress wood. Spanning approximately 260 square meters (equivalent to 160 tatami mats), this impressive wooden structure has no supporting pillars in its center. The bathhouse contains four different hot spring sources: "Netsu-no-Yu" (Hot Bath), "Shibu-Rokubu-no-Yu" (Four-Six Bath), "Hie-no-Yu" (Cool Bath), and "Shika-no-Yu Taki" (Deer Bath Waterfall), each with distinct temperatures and characteristics. The Netsu-no-Yu features a rare "ashimoto yushutsu" system where hot spring water naturally emerges from the bottom of the bath, providing fresh 100% source water flow.

Mount Hakkoda is located within Towada-Hachimantai National Park and is known as one of the world's heaviest snowfall regions, with annual snowfall reaching approximately 17 meters and maximum snow depth of about 23 meters. Despite the harsh natural environment, the facility operates year-round, offering spectacular seasonal scenery: frost-covered trees and snow landscapes in winter, fresh beech greenery from spring to summer, and stunning autumn foliage. The ancient saying "Three cycles of ten days will cure all ailments" reflects its long-standing reputation as a therapeutic hot spring destination attracting visitors from across Japan.

The famous woodblock print artist Munakata Shiko loved Sukayu and created artworks while taking hot spring therapy here. Adventurers Miura Keizo and his son Miura Yuichiro also cherished the Hakkoda Mountains and frequently visited Sukayu. The water quality features strong acidity with pH 1.5-2.0, and as the name suggests, tastes more sour than lemon when tasted, with characteristic sulfur odor and milky white cloudy appearance. It is recognized as a "therapeutic hot spring" effective for neuralgia, rheumatism, skin diseases, gynecological conditions, gastrointestinal disorders, and various other ailments.

The accommodation facility has 139 rooms divided into two sections: the "Ryokan-tou" (Inn Wing) with a retro Showa-era atmosphere, and the simple "Toji-tou" (Hot Spring Therapy Wing) designed for self-catering and long-term stays. The therapy wing includes kitchen facilities, allowing stays of 10 days or more. The facility also features attractive cuisine using seasonal produce from Aomori's mountains and seas, utilizing abundant local ingredients.