In a letter to Sō Sadamori issued on the 15th of the 7th month, the Joseon claimed that Tsushima belonged to Gyeongsang Province and asked him to leave the island, either by coming to the Korean Peninsula or by retreating to mainland Japan. In the 9th month, a man who claimed to be an envoy of Sō Sadamori arrived in Korea. The conditions he presented seemed unsatisfactory to the Joseon. Taejong made similar demands of the envoy in the 10th month. According to the article on the 10th day of the first leap month of 1420 of "Sejong Sillok", the same self-claimed envoy agreed to Korea's proposal to put Tsushima under the rule of Gyeongsang Province. On the 23rd of that month, the Korean court approved of this agreement. However, in later negotiations it was revealed that the envoy was not actually a representative of Sō Sadamori.