do kyung soo  is an incredibly immature young man who is useless at his job as a director at DN Group, where the chairman is his father ( Do Seok-chul). kyung-soo has a longstanding rivalry in work and love with cousin byun baek-hyun, as baek-hyun is a mature, hardworking, and seemingly perfect executive, and the two both have a romantic history with kim ji-sook. Spunky and tough kim tae-yeon  is struggling to find full-time work because of her juvenile delinquent record and poor academic background. After giving the hiring directors a piece of her mind during a job interview at DN Group, she is surprised to find herself hired by baek-hyun (who was captivated by her interview) to be the secretary to kyung-soo. Determined not to be fired from her first professional job, ji-sook works diligently at putting up with kyung-soo's childishness and keeping him in check. As their working relationship progresses, they earn each others' trust and friendship, and ji-sook helps kung-soo deal with his phobias and prove himself capable of becoming DN Group's successor. Things get more complicated when kyung-soo and baekhyun both fall for ji-sook, who doesn't want to get mixed up with either of them... or does she?