Singer and actor Seo In Guk has once again proven himself to be a top-class singer.

His duet with singer Zia was an unannounced, surprise release. Titled, "Loved You", the song is sweeping all the top online music charts, including MelOn, Mnet, Bugs, Soribada, Ole Music, Naver Music, Daum Music, Monkey3, and Genie, as the #1 song.

"Loved You" is a sad R&B ballad that tells of the heartaches that a couple experiences through a breakup. The song was composed by Hwang Se Jun and Melodysign.

Seo In Guk reinvented himself as a marquee actor through tvN's "Respond 1997". He was also cast on "The Master's Sun" and the movie No Breathing.