Lee Kwang Soo opened up about his hard effort for the new KBS sitcom 'Sound of Heart'.

During the press conference on December 8, Lee Kwang Soo revealed, "The director told me that there'll be skin exposure so I worked out a lot. Kim Jong Kook hyung also helped me a lot on working out, but after seeing the web version, I thought, 'Did I work that hard for that? It wasn't really necessary.'"

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He continued, "But there are still a lot of unrevealed scenes with exposure, so please look forward to it."

The first episode of 'Sound of Heart' will broadcast on KBS on December 9.