While the years of his birth and death are not known, in 'Homyo of the Nanjo family' (homyo is a Buddhist name given to a person who has died or has entered the priesthood) included in "Ueshinanjoki" we can find a homyo that reads 'Gecchujoshin-shinji Chisokuin' (月中常心信士 知足院), which is thought to be Sosho.
没年、生年とも不詳だが『羽衣石南条記』所収の「南条家法名」には、「月中常心信士　知足院」とあり、宗省のことを指していると思われる。