Young-hu Kim and Shinwa both have worked for what music company? 
Young-hu Kim:  He works mainly with SM Entertainment artists, and has written songs for Girls Generation, Exo, TVXQ, BoA, Shinee, f(x), Super Junior, Shinhwa, and Fly to the Sky. Shinhwa:  Launched by SM Entertainment on 24 March 1998 and now managed by Shinhwa Company, the group is the longest-running boy band in the history of K-pop and one of the pioneers of the K-pop idol culture.
SM Entertainment