~~ Istoric ~~

2012: Debut
The eight members were introduced individually through eight different teaser photos released from July 16, 2012 to July 23, 2012 (in order: Seolhyun, Choa, Hyejeong, Chanmi, Yuna, Mina, JiMin & Youkyoung .
AOA is a dance group, with some members also playing instruments. Youkyoung (or "Y") is listed as a "half-angel/half-mortal", because she is only a member of the band half, playing the drums, resulting in AOA saying they are a "7+1" group.
According to FNC, the seven "full angel" members (Seolhyun, Choa, Hyejeong, Chanmi, Yuna, Mina, and leader Jimi) looked on the human world through their crystal ball, and fell in love with the music of humanity. Youkyoung, the "half-angel, half-mortal", also referred to as the key keeper, became curious about the human world and used the key to visit it with the other angels.
The first music video teaser for "Angel's Story" was released on July 24, 2012 and the second teaser was released on July 26, 2012. "Angel's Story" was leaked on July 28, 2012 with 2 days before the official release.
The music video for "Elvis" was released on July 30th, 2012.