Founded in 1662, Matsuzakaya Honten is one of Hakone's most distinguished heritage ryokan, immortalized in Utagawa Hiroshige's ukiyo-e woodblock prints. Ashino-yu, at approximately 870 meters elevation, was counted among the "Seven Hot Springs of Hakone" during the Edo period and was designated as Kanagawa Prefecture's first National Health Resort Hot Spring Area in 2015. Its most exceptional quality lies in the rare combination of three "beauty skin" mineral types — sulfur, sulfate, and bicarbonate — all naturally balanced in a single source. Approximately 260 liters per minute well up from just 60 meters below the surface, delivered as 100% source-fed flowing water without any dilution or temperature adjustment. The mystical quality of the water, which changes color with temperature and weather conditions, adds to its allure. Twenty-two rooms spread across six distinct buildings dot the four-thousand-tsubo grounds, creating a serene retreat far removed from Hakone's tourist bustle. With over 360 years of history, the bathing halls offer one of the most authentic hot spring cultural experiences in all of Hakone.