L as Lee Hyun Soo

Hyun Soo has been named the 21st century prodigy of the marketing industry. He has a creative mind that is able to come up with award winning creations and marketing ideas. One day he realizes that he has lost his sense of creativity and decides to take 3 month vacation from work in order to find his inspiration again. He disguises himself as Chan Sol and enters the OZ company to become an employee.

Bae Suzy as Jang Ma-ri

Ma-ri tries to stay afloat by managing her late brother's advertising company OZ. Despite her hard work, she finds it difficult to run the company as she continues to lose customers to the point that she can barely pay her workers/friends. She is a hard worker who is always optimistic. One day, during heavy traffic, she meets Hyun Soo who later arrives at her house offering to buy OZ. Due to this offer, she automatically assumes that Hyun Soo is a cold hearted man with evil intentions; thus, having a bad first impression of him. She has no idea that Chan Sol is Hyun Soo in disguise when he comes to work for her company.

Shin Won Ho as Lee Chan Sol

Chan sol is Hyun Soo's alter ego. He enters the OZ company as Chan Sol and forms a close bond with his coworkers particularly his boss, Ma-ri.

Lee Min Ho (1993) as Park Hee Chul

Works at OZ as the creative director of advertising. He is a very loyal and serious person. People who don't know him describe him as a person who has a cold robotic personality. Only his colleagues know the real him and sees him as a big brother. He is very close to Ma-ri which causes him confusion on how he really feels about her.

Ham Eun Jung as Yoon Baek Hee

Works at OZ as a creative visual designer and is Jang Ma-ri's bestfriend since college. She has a playful and active personality and often acts like a teenage girl. She likes to use her designs and drawings to express her inner thoughts and emotions.