The story of a man who cannot forget his first love from 10 years ago and is given the chance to redo history as he returns to the past. Kang Shin Woo (Lee Jung Shin) is a math teacher with a good looking appearance. He has not forgotten his first love Han Ji Soo (Lee Yul Eum) for the past 10 years. By an accident, he travels to the past when he was a high school student. There, he meets his younger self (Seo Ji Hoon). Kang Shin Woo struggles to make the younger Kang Shin Woo’s love come true.