Yun Mu Kwan was originally a judo school started by Kyung Suk Lee; during the Japanese occupation of Korea, instruction in judo was allowed. Meanwhile, Chun Sang Sup was a college student in Japan where he studied both karate and judo. It is generally believed that Chun studied Shotokan karate under the tutelage of that system's founder, Sensei Gichin Funakoshi (though other sources suggest that Chun may have studied under Toyama).