Go Yoo and Joon-hee are two friends in high school with different tastes. So-yeon is the new girl that everyone is talking about. When Joon-hee becomes sick, Go Yoo gives him a kidney transplant and Joon-hee experiences cellular memory syndrome. Suddenly Joon-hee becomes like Go Yoo, and vice versa. The two friends become rivals for So-yeon’s love in the midst of their friendship. 15 years later, So-yeon and ‘Dr. Go’ coincidentally meet again.