Lee Chang-ho
Yun became a professional in 2001. He was promoted to 3 dan in 2004, 4 dan in 2005, and 5 dan in 2007 after winning the Guksu title. He is currently 9 dan. Yun broke a record in 2002 when he qualified for the first round of the 7th LG Cup. It was the shortest time between becoming a pro and entering an international tournament (3 months). In 2003, he just missed out on challenging Lee Chang-ho for the Kisung title when he lost to Cho Hunhyun in the challenger final, two games to one. In 2007, he won the Guksu title 3 to 1 over Lee Chang-ho.