Sokin (year of birth unknown - 1455) was a merchant in Hakata in the mid-Muromachi Period. His son was So-seijun.
He was active in trade with the Ming Dynasty in China and the Yi Dynasty in Korea, firstly under the Kyushu Tandai (local commissioner) Mitsuyori SHIBUKAWA, and then under the Otomo clan. In 1419, he received and entertained Song Gik-yeong, the delegate dispatched from the Yi Dynasty in Korea after the foreign invasion of the Oei Era, and accompanied him to Kyoto to play a reconciliatory role between him and Bakufu (Japanese feudal government headed by a shogun). As an envoy of the sixth seii taishogun (literally, "great general who subdues the barbarians") of Muromachi bakufu, Yoshinori ASHIKAGA, as well as of other feudal clans, such as the Shiba clan, Shibukawa clan, Otomo clan, and Shoni clan, he worked as the representative in trade with Korea, and in 1425 he was granted special privileges in trading (Tosho), which was the sign of trade permission with Korea, and was appointed as Jutoshonin (Japanese given Korean government evidence to be granted special privileges in trading). In 1436, he was also involved in the project of Kenminsen (envoy ships dispatched to Ming China).
When Emperor Munjong (Korea) ascended to the Throne (1450) as the 5th Emperor of the Yi Dynasty in Korea, he hastened to visit Korea to celebrate the enthronement.
It is said that he was a Buddhist monk of Myoraku-ji Temple (Fukuoka City) and a monk of the same name appears in the diary of Kugyo (Court noble) Noritoki YAMASHINA, "Noritoki Kyo Ki" (diary of Noritoki YAMASHINA).