In this, Kang Shin-Woo (Lee Jung-Shin) is a math teacher with a good looking appearance. And Han Ji-Soo (Lee Yeol-Eum) is his first love for the past 10 years but he has not forgotten. 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.