[3][4] Before debuting with SG Wannabe he had worked as a backing vocalist and vocal coach and was a frequent performer in the Hongdae area's club scene.

[6] With the impending departure of Chae Dong-ha from SG Wannabe, the group's label Mnet Media secretly held an audition to find his replacement and Lee heard about it by word of mouth from notable producer and composer Kim Do-hoon, now co-CEO of RBW.

Because Chae had abruptly left the group in the midst of preparing for the album, Lee only had several months to rehearse and record his parts and film the music video for the lead single "Lalala".

[10] The songs "Station" (정거장) and "Ten Reasons I Love You" (그대를 사랑하는 10가지 이유) remained in the Gaon Digital Chart for over two months.

[13][14] In January 2013 Lee enlisted for mandatory military service and was initially designated as a "celebrity soldier" assigned exclusively to public relations duties.

[16] With SG Wannabe preparing their comeback, he focused his attention on group activities as the members were much more involved with the production and composition process.

[24][25] For the early half of 2021 Lee was a guest DJ for various radio programs, including covering for Jun Hyo-seong when she was in self-isolation after coming into contact with a suspected COVID-19 case.

[26] He was cast in Marie Antoinette as the eponymous character's friend Swedish nobleman Axel von Fersen the Younger; the critically-acclaimed domestic production ran for the third time and opened on July 13.