This is a "You're Beautiful", a Korean drama fanfiction.
Go Mi Nam begs his younger sister Go Mi Nyu to accompany him when he goes to sign a contract with the band A.N.JELL. When he is caught by the leader of the band, Hwang Tae Kyung, he is forced to sing, but unfortunately panics. And so his sister coaxes him into singing by singing a song herself, resulting in Tae Kyung to want both of them in the band!
Meanwhile, Mi Nyu seems to have fallen for gentle and kind second member of the band, Kang Shin Woo, while Tae Kyung will do anything to make her his. Can Mi Nyu survive the explosion of feelings in her heart?