Tae Seok, Ji Yoon and Min Soo were best friends in high school. Min Soo likes Ji Yoon, but Ji Yoon and Tae Seok like each other. When he sees them kissing, he attempts suicide in front of them, leaving Ji Yoon and Tae Seok feeling guilty.
7 years later, Tae Seok is a CF producer and he has a new best friend named Dong Hwa. Strangely enough, he meets Ji Yoon again, but as Dong Hwa's girlfriend. Additionally, Minsoo's sister has a one-sided crush on him. Tae Seok will have to decide between them, but he doesn't want to make the same mistake as before.
But when Dong Hwa discovers Ji Yoon's and Tae Seok's past from Min Soo's sister and realizes that Ji Yoon still loves Tae Seok, Dong-hwa experiences the same feeling of betrayal as Min Soo.