[8] He also worked as a "guide vocal," singing demos of songs that would ultimately be recorded by other artists including TVXQ, g.o.d.

[10] K.Will released his debut album, Left Heart (왼쪽 가슴), on March 6, 2007 via Bang's label Big Hit Entertainment.

Producer Park Jin-young composed the album's title song, which reached number 3 on the Melon digital chart shortly after its release.

[11][12] In January 2008, K.Will left Big Hit and joined his agent Kim Shi-dae's new company Starship Entertainment.

[23] On January 21, 2011, K.Will released the single "Amazed" (기가 차), featuring rapper Simon D and Hyolyn of girl group Sistar.

[27] The single also marked the first time K.Will won first place on a South Korean music chart television show, with his April 3 win on Inkigayo.

[28] K.Will held his third solo concert in Seoul on June 25, 2011, featuring guests Wheesung, Lee Hyun and Sistar.

[29] He held his annual Christmas concert over three days in December, featuring special guests Wonder Girls and Orange Caramel.

[30] He also finished out the year as a contestant on the TV show Immortal Songs 2, which he left in January 2012 after setting a record of five consecutive wins in the singing competition.

[35] The music video, starring Ahn Jae-hyun, Seo In-guk, and Dasom, received both domestic and international attention for its twist ending featuring a same-sex crush.

[41] The lead single, "You Don't Know Love" (촌스럽게 왜 이래), was his third number 1 hit on the Gaon Digital Chart.