A 28-year-old female prosecutor Min-seo is just about to go out with Jun-hyun, a good looking prosecutor whom she has had a crush on since high school. With a successful career and her soon-to-be boyfriend, it seems like she is the happiest woman in the world. However, she suddenly time travels to her high school life while she is chasing a male suspect named Sang-woo; he was a senior in her high school. She genuinely does not want to relive her high school life because it was just the stereotype of a nerd. With a strict moral code as a prosecutor, a teenager's appearance, and two attractive men, namely Jun-hyun and Sang-woo, around her, her second high school life will be nothing like her previous one.