I have never heard of kung sul. I have heard of Kook Sul. Could this be what you are referring to? It is Korean, has punches, kicks, weapons, and joint locking techniques. It seems similar to Hapkido to me. This is all coming from someone who saw one class, so take it for what it's worth. If this is not what you were looking for, then nevermind. Try this site. http://www.kuksoolwon.com/Main.htm