Song Ju and Jeong Seo who have lost a father and a mother respectively spend their childhood together like real siblings. Song Ju is there for Jeong Seo whenever she feels lonely and has a hard time, and Jeong Seo also relies a lot on Song Ju. However, after Jeong Seo's father gets married to Tae Mi Ra, Mi Ra and her daughter Yu Ri keep harassing Jeong Seo out of jealousy. Tae Hwa, Yu Ri's rough and wild older brother, has a crush on Jeong Seo who is pure and kind unlike him.
The relationship of childhood sweethearts Cha Song Ju and Han Jeong Seo becomes complicated when Jeong Seo's father remarries. Along with a new stepmother, Jeong Seo also has a new introverted stepbrother, Han Tae Hwa and a scheming stepsister, Han Yu Ri. Gradually, Tae Hwa falls in love with kind-hearted Jeong Seo and Yu Ri decides to pursue Song Ju. Nothing can shake the bond between Jeong Seo and Song Ju, however, not even Song Ju's departure to study abroad in America. On the night of his return, however, Jeong Seo is mysteriously hit by a car and believed dead. Having lost her memory in the crash, she is taken in by Tae Hwa, who relocates and gives her another name. Five years later, on the eve of his engagement to Yu Ri, Song Ju sees someone who looks exactly like his lost love Jeong Seo.