A.N. JELL is a very successful boy band formed by three young men. The managers have decided to add a fourth member and have chosen Mi nam. However, he is forced to put aside his dream when he must leave to the United States to undergo surgery. Therefore, his twin sister Mi nyu will pretend to be him while he recovers.
The arrival of Mi nyu, under the identity of her brother, will not be well received by its members, forcing her to overcome her shyness and innocence. Band members Sin woo and Jeremi try to get along with the new member but consider him strange. However, the band leader Tae kyung, cannot stand ‘his’ presence, making living together very difficult. Over time, Mi nyu will awaken deep feelings in each of the three boys especially Tae kyung, who will discover his secret.