[1] The song was written by composers veterans Andreas Stone Johansson and Ricky Hanley, in collaboration with Korean lyricist Sarah Yoon and Chinese lyricist Liu Yuan.
The song talks about a man who recalls with nostalgia the relationship with his former girlfriend and his desire to return to it, but cannot do so because of the shame and guilt.
On December 4, 2013 both versions of the videos were announced, at 8:00pm (KST) and were released on video-sharing websites.
[3] The music video was directed by Jo Soo-hyun, and was filmed in November in Paju, Gyeonggi in a study in Ilsan.
The song was also included in the set-list of the winter festival of the group with his classmates seal f(x) SM Town Week: Christmas Wonderland on 23 and 24 December.