After ending their promotions for the Niga Mwonde mini-album, leader Jaehoon left the band citing personal reasons; no other information was disclosed. On October 28, 2011, the band announced a new member would be joining them for their upcoming single, Keon U who is well known as the son of famous composer, Park Kwang-hyun. Another new member, Hanbyul was also announced on November 3 as the new appointed leader of the group alongside teaser photos of the rest of the band, thus making them a six-member group.
