Eun Ha-won is a high school student who dreams to be a teacher, but she needs money for her education. One day, she meets the Chairperson of the Kang enterprise who offers her the chance to live in his house if she accomplishes the mission of reuniting his three grandsons, under some conditions, such as she cannot date anyone among them. At the Sky House, she meets Kang Ji-woon, a soft hearted but lonely and wild-child rebel, Kang Hyun-min, a playboy plutocrat who does whatever he wants, Kang Seo-woo, a top singer-songwriter who is gentle and kind to Ha-won, and finally Lee Yoon-sung, the Chairman's secretary and their bodyguard.