AJ (Real Name: 이기광, Pronounced "Lee Gi Kwang") was a solo-artist under Cube Entertainment. He began his singing career training under JYP Entertainment for four years, but was then transferred to their sister entertainment company, Cube Entertainment, where he debuted with his first mini-album, First Episode A New Hero, Released on 10 April 2009. He began promotions for the mini-album with the song "댄싱슈즈" (Dancing Shoes), and followed up promotions with "눈물을 닦고" (Wipe The Tears). The mini-album also contained the song "2009", which featured 현아 of 4minute, who also appeared in the music video for "댄싱슈즈" (Dancing Shoes).
A few months after AJ finished promotional activities for his mini-album, he debuted in the Cube Entertainment boy group, B2ST, where he is known by his real name, 이기광.