Shim Bo-nee: Starring Hwang Jung-eum

She is attractive, well-groomed, nice, and gentle. Even when she’s under the threat of being evicted for not paying the rent or getting her electricity and gas cut off for unpaid utility bills, she keeps a positive outlook on life. She is a talented programmer at a small software company and juggles marketing and business development duties on top of her coding job. But if there is one shortcoming that she has it is the fact that she is a very superstitious person. After she lost her parents in a car accident and when her younger sister fell into a coma in a separate accident, she started seeking advice from fortunetellers. One fortuneteller tells her that to save her sister, she would have to sleep with a man born in the Year of the Tiger. So upon getting hired at Jaejae Factory, she aggressively pursues Soo-ho because he is born in the Year of the Tiger.

Jae Soo-ho: Starring Ryu Joon-yeol

As the CEO of Jaejae Factory, the biggest game software company in the country, he is incredibly smart with a decisive personality. He believes that all problems can be solved with logic and a pragmatic approach. He dated Seol-hee when he was studying in America. She was like a breath of fresh air. But Seol-hee suddenly disappeared without even a good-bye and it left him with trust issues with women. Bo-nee was someone that Soo-ho thought was a top-notch programmer and relied on logical reasoning. But he discovered that she was obsessed with superstitions.

Choi Gun-wook: Starring Lee Soo-hyuk

A professional tennis player ranked 33 in the world and winner of the 2015 Australian Open. He has a perfect athletic build for tennis in addition to his movie star looks. His sunny and confident personality is also perfectly tailored for the limelight as a star athlete. He rarely gives interviews so his private life is a mystery. After his parents divorced, he had never seen his father since. So he returns to Korea to meet him. Bo-nee used to live on the lower floor of his childhood home and he tracks her down but she cannot recognize him. As they are currently neighbors in the same building, he sees her a lot and finds himself falling in love with her.

Han Seol-hee: Starring Lee Chung-ah

She’s an alpha girl who is sophisticated, elegant and astute in business. She does not wear makeup when she is not at work and has a tomboyish personality. She is the second child of a world-renown physicist and enrolled in the physics department of an elite university in the U.S. but she found physics boring and switched to business school. She got a job at IM, a global sports management company, and started managing tennis player Gun-wook, a rising star. She returns to Korea to continue managing Gun-wook, and there she is reunited with Soo-ho, a college friend. While working together with Soo-ho to develop a game, she found herself attracted to him even though he was mostly like a little brother to her.