Kim Sŏngil was the vice ambassador on a Korean mission to Japan in 1590 led by Hwang Yungil. The mission was dispatched in response to demands for tribute from Toyotomi Hideyoshi, and was ostensibly to congratulate Toyotomi Hideyoshi on his unification of Japan. It was also aimed, however, at ascertaining as much as possible about Hideyoshi's plans to invade Korea, and to perhaps negotiate terms to stop the invasion (they were unsuccessful in the latter).
Kim was a direct disciple of Yi Hwang, perhaps the most famous Neo-Confucianism scholar in Korean history. He, along with Hŏ Sanjŏn (an assistant to the embassy), and other scholars on the embassy met with Japanese scholars such as Fujiwara Seika, and shared valuable books on Neo-Confucianism. This is said to have been a significant event in the introduction of Neo-Confucianism into Japan.
- Doyoung Park, "A New Perspective on the Korean Embassy (Chôsen Tsûshinshi): The View from the Intellectuals in Tokugawa Japan," Studies in Asia Series IV, 3:1 (2013), 13-14.