Singer Roy Kim is the voice behind Lee Jong Suk�and Suzy's love theme for the 'While You Were Sleeping' OST.�

SEE ALSO: Kep1er's agency responds to reports of disbandment

Roy Kim's soft vocals is perfect for "You're Lucky", an acoustic ballad. In the drama, it acts as Jaechan's (Lee Jong Suk) affectionate feelings for Hongjoo (Suzy), and viewers were interested in the track immediately after hearing it in the series' teasers.

A rep stated, "Despite the long recording, Roy Kim put his all into the perfection of the song. He expressed Jaechan's feelings in his own style like nobody else could."

Check out the song above! Have you been watching 'While You Were Sleeping'?