Lee Hyunki (19 years old) a Violin/Cello major at Seoul University and his little sister Lee Mihwa (16 years old). At the age of 6 Mihwa, got into a car accident and suffered brain damage. In short, physically she is 16, but mentally she learns very slow and is at the age of 10. Shortly after her accident, their father abandons their family because he couldn't handle Mihwa being mentally challenged. 3 years later, their mother dies of cancer and from then on they live with their abusive father who blames Mihwa for everything. This causes a whole bunch of problems for Hyunki and Mihwa, so Hyunki takes matters into his own hands and make his sister the number 1 priority. Everything, from school, work, and even his life comes second to her. Since his sister's accident and moving in with their father, Hyunki noticed how the world had no shred of compassion for his sister. People always treated her like she was stupid, they beat her and when he tried to protect her, they beat him as well. From that day on, he became very cold and was only nice to you if he felt like he could trust you. While in college, he meets SNSD and takes a particular interest in Yuri. Due to his cold nature, she feels that he is arrogant and impolite. But once she finds out his secret, will things chage for the better or for the worst?