쌍둥이 남매 고미남, 고미녀는 고아원에서 함께 자랐다. 미남은 곧 데뷔를 앞둔 보이밴드에 합류하였지만 불의의 사고로 활동하지 못하게 되고, 미녀는 오빠가 어렵게 잡은 기회를 놓치지 않기 위해 한 달간 미남으로 살기로 한다. 매사에 서툰 미녀는 이내 미남의 주변 사람들에게 의심받고, 같은 밴드 멤버인 태경, 신우, 제르미에겐 곧 여자인 것을 들킨다. 하지만 미녀는 특유의 긍정적인 에너지로 사람들의 마음을 얻고, 멤버들은 어느새 미녀에게 특별한 감정을 품게 된다.
Mi Nyeo has a twin brother, Mi Nam. They grew together at an orphanage. Mi Nam has been chosen to be a member of a boy band, but he can't work as a singer due to an accident. So Mi Nyeo pretends to be her brother and starts to live as Mi Nam, the idol singer. The boy band has three other members: Shin Woo, Tae Kyung, and Jeremy. Shin Woo is a musical genius and the most popular member. Unlike the artistic and sensitive Shin Woo, Tae Kyung is more like a businessman and is hardly moved by anything. And Jeremy is an optimistic person who gets along with everyone. Mi Nyeo, living as Mi Nam, has to work with them. However, she is not sociable as she has lived all her life cut off from the world. So living as an idol singer is hard for her.