He was a member of the South Korean boy band 100% under the label of TOP Media, as the leader and vocalist.

In 2009, Seo was featured during Andy's promotion for his song "Single Man", along with Jumper's second member Park Dong-min (Korean: 박동민).

[6] In 2013, Seo made a cameo in KBS2's drama, Marriage Clinic: Love and War 2 (Korean: 부부클리닉 사랑과전쟁2).

[7] Seo was chosen as a member of the group 100%, the seven member South Korean boy group that debuted in September 2012 under Andy Lee's company TOP Media with their first single album We, 100%.

On March 25, 2018, Seo was found in his home in Gangnam in a state of cardiac arrest.