Shortly after he had completed his military service, he featured on Kim Jang-hoon's single "Breakups are So Like Me". During live performances of the song on "Music Bank" and "Show! Music Core", his part was performed by bandmates Yesung, Eunhyuk and Shindong. Also he wrote the lyrics of Orange Caramel's "Shanghai Romance" on October 13, 2011, which peaked at number eight on the Gaon Digital Chart.