The So clan dispatched false royal envoys for purpose of trading, and additionally, they sent such envoys in order to gain more advantages in important negotiations such as the peace negotiations of the Sanpo War and the Saryang Incident.
また交易目的だけではなく、三浦の乱や蛇梁倭変の講和のような重要な交渉時にも、有利な交渉を目論み偽の日本国王使を派遣している。