When Gong Chan (Lee Dong Wook) meets the lively and beautiful Yoo Rin (Lee Da Hae), he finds out that she has connections to his missing cousin, whom his grandfather has been searching for. He asks Yoo Rin to lie about being his long missing cousin until he can find his real cousin. She says yes, but soon their feelings for each other get in the way of their plans. Gong Chan's friend, Jung Woo (Lee Joon Ki) falls for Yoo Rin while Gong Chan's ex-girlfriend, Seo Hyun (Park Si Yeon), a pro tennis player, tries to win him back. Will the two ever tell each other how they feel? Will Gong Chan ever find his real cousin?
As Gong Chan stays determined to set things right, President Seol's stubbornness doesn't seem to be subsiding.
When President Seol begins to get impatient and plans an immediate trip to Japan to meet Yoo Rin's "foster father", Yoo Rin resorts to desperate measures.
Madam Jang and Il Do are preparing for their wedding while Gong Chan must manage Yoo Rin's drunken antics and Sae Hyun's struggle for attention.
While Jung Woo is trying to get President Seol's consent to date Yoo Rin, Madam Jang tries to get Jung Woo's mother to look favorably upon Yoo Rin as well.
When Sae Hyun finds out some important information regarding Gong Chan's family, she sets up a meeting with President Seol.
Gong Chan and Yoo Rin begin to get closer as she plays pranks on him. Sae Hyun is less than pleased with their newfound "sibling" bond.
Yoo Rin flees from her father's loan sharks thanks to the help of Jung Woo. Meanwhile, Gong Chan continues to find clues about his missing cousin.
Yoo Rin accepts the part of Gong Chan's long lost cousin. Sae Hyun continues to get Gong Chan's attention and forgiveness.
As Sae Hyun and Gong Chan try to start fresh, Sae Hyun struggles for his grandfather's approval. Meanwhile, Yoo Rin takes a fall for Sae Hyun to help her escape the media.
Jung Woo finds out about more than one of Yoo Rin's secrets, thanks to his keen observations. Yoo Rin also deals with some unreasonable people to help her father.
As Sae Hyun and Gong Chan's relationship is displayed more and more, Yoo Rin and Jung Woo go to the arcade to relieve some stress.
Gong Chan and Yoo Rin visit the grave of her "parents" and end up relying on the help of some friendly strangers for one night.
As Yoo Rin tries to see Gong Chan as a cousin, the family sets her up with a surprise meeting. Meanwhile, the inauguration for Yoo Rin into the company is around the corner.
When Gong Chan decides not to leave, he and Yoo Rin have a different plan, but Jung Woo and Sae Hyun are still determined to get their way.
Two years have passed as we see the result of Yoo Rin's decision and how it has affected the people involved.
When Gong Chan learns Yoo Rin is fluent in other languages, he hires her as a translator for an important business meeting.