A hidden hot spring located at an elevation of approximately 750 meters on the southwestern slope of Mount Eboshi, one of the five peaks of Mount Aso. First established in 1803 (Bunka 1), it boasts over 220 years of history. During the Edo period, bathing was reserved exclusively for samurai of the Kumamoto domain, and it was opened to the general public from the Meiji era onward, flourishing as a therapeutic bathing destination. The name 'Jigoku' (Hell) comes from areas near the springs where volcanic gases prevented plant growth. The main attraction is 'Suzume no Yu,' an exceptionally rare open-air bath where the hot spring water bubbles up directly from the bottom of the bathing pool. Known as a 'miraculous spring,' bathers can soak in the raw, untreated source water with no heating or dilution. The facility has three different spring sources with 11 baths across four locations, each offering unique water qualities and atmospheres. In 2016, the Kumamoto earthquake and subsequent mudslides buried approximately 70 percent of the grounds, but Suzume no Yu miraculously survived. Day-trip bathing reopened in 2019, and the inn was renamed from 'Seifuso' (Clear Wind) to 'Seifuso' (Blue Wind), expressing the wish to be free from water-related hardships. Visitors can enjoy a one-of-a-kind experience soaking in the sulfurous mud bath bubbling from below, with natural mud packs also available.