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 Yeol-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.