Shuseikan is a solitary inn located in the Yashiki village of Akiyamago, at the northernmost tip of Nagano Prefecture, standing at approximately 700 meters elevation along the Nakatsu River Gorge in a remote mountainous area. Positioned in a deep valley between Mt. Naebasan (2,145m) to the east and Mt. Torikabusan (2,038m) to the west, it serves as a central hot spring inn in Akiyamago, which has been selected as one of Japan's Top 100 Hidden Regions.

Historically known as the "Hidden Bath of the Heike Clan" or "Kobo's Sealed Spring," this historic hot spring carries the legend of the Heike clan refugees. According to legend, during the Bunji period (1185-1189), Taira no Katsuhide was defeated by Minamoto no Yoritomo, and his clan fled to this area to live in hiding. Akiyamago is known as a heavy snowfall region, and due to its historically inconvenient transportation, unique living customs have been preserved. Today, it remains a precious hot spring destination where visitors can fully experience the atmosphere of a hidden region, as a quiet solitary inn built right beside the clear Nakatsu River.

The most distinctive feature of the hot spring is that it is the only sulfur spring in Akiyamago. With its complex composition as a sulfur-containing sodium-calcium-chloride-sulfate spring, the mystical waters change color from transparent to emerald green to milky white depending on the weather and sunlight. The distinctive scent from hydrogen sulfide and the dancing mineral deposits create an atmosphere truly befitting a hidden region hot spring.

The open-air bath, located in front of the parking area with an extremely open design resembling a pond, is remarkably distinctive. The indoor bath, called the "Observation Bath," features large glass windows allowing bathers to enjoy views of the Nakatsu River Gorge while bathing. Selected as one of Japan's Top 100 Famous Hot Springs, it is also a genuine therapeutic spring with a hot spring therapy instructor on-site.