Sanyo-so is a ryokan-style inn nestled at the foot of Mt. Genji in Izu Nagaoka, Shizuoka Prefecture. The inn occupies the site of a villa constructed in 1929 for Hisaya Iwasaki, the eldest son of Yataro Iwasaki, the founder of the former Mitsubishi conglomerate. The name “Sanyo-so” is a reference to a set of three mottos written by Su Shi, a writer of Song-era China with diverse tastes and talents. These mottos inspired the Iwasaki family to borrow them as their own, and when ownership of the villa later changed hands, the name was carried over as well. The villa opened for business as a ryokan inn in 1947. Having started with 15 buildings, today it now has 37 buildings.