Seo In-guk

 Lee Ha-na

 Lee Soo-hyuk

 Lee Yeol-eum

Lee Min-seok is a high school student and varsity ice hockey player. He and his older brother Hyung-seok look very much alike, despite their nine-year age gap. When he gets a mysterious phone call from Hyung-seok telling him to impersonate his brother at the latter's new job, Min-seok is forced to pretend to be a high-ranking executive at an IT conglomerate. Living a double life while unaware of the rules within the Korean workplace, Min-seok learns how to navigate his way in the world of adults with the help of Jung Soo-young, a temp with an odd personality whom he eventually falls in love with.