During 2005–2010, Kim has had two solo songs from SS501 albums: "Rize Up" from Kokoro, and "Please Be Nice To Me" from SS501 Solo Collection. In 2008, he released "Thank You" digital single, a theme song from We Got Married and was also included in SS501 mini album Find. In 2009, he contributed two soundtracks from Boys Over Flowers including the acoustic version of "Because I'm Stupid"" and "A Thing Called Happiness". He, then released a DVD entitled Goodbye Yoon Ji-hoo, marking the end of his character role in Boys Over Flowers, and coming back as the leader of SS501. In 2010, he contributed "One More Time" from his drama Playful Kiss.