Lee Kwang Soo discussed Song Joong Ki's cameo appearance in the new KBS web drama/sitcom 'Sound of Heart'.

At the press conference on December 8, Lee Kwang Soo said, "Song Joong Ki immediately accepted my request for a cameo even before seeing the script. I'm very thankful for such friend." He continued, "I actually didn't know that many female staff members existed until that scene [with Song Joong Ki]. There were also some who I've never seen before." 

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Director Ha Byung Hoon agreed and said, "I didn't realize that we had that many staff members until Song Joong Ki came to the set. There were about 2 times more people than usual, and they were staring to the point that it was scary." 

He also added, "Song Joong Ki worked very hard, and he prepared a lot. He also took pictures with all the staff members before leaving. I regret not taking one with him."

The sitcom version of 'Sound of Heart' will broadcast on KBS starting December 9.