The sub-unit debuted with their mini album titled Fly High in January 2013.

[1] Prior to their debut as a subgroup, the duo had performed new songs such as "Crying" and "You Look Good" during Infinite's concerts and had already received much attention.

Although they had been releasing new songs during concerts, Woollim Entertainment only announced that they will be promoting as a sub-unit in 2013 after finishing up with Infinite's activities in Japan.

[2] They also performed, "Without You", a song from their debut album at the “Infinite Concert That Summer” on August 8, 2012.

[5] They also held a press conference and a showcase on the same day at AX Korea, in Seoul.