Regarding the web drama based on the web toon of the same name, Lee Kwang Soo said, "The only web toon I made sure to read all of was 'Sound of Heart.' There were also a lot of people around me who liked it, so when I was talking about this to people, many congratulated me. Kim Jong Kook congratulated me and was happy for me; on top of that, he appeared as a cameo, so I want to say thank you to him."
Aw, always making sure to thank his fellow 'Running Man' members! How sweet.