Wi Mae Ri is a stubborn woman and the daughter of a failed businessman without much experience in dating. She starts to date tough rocker Kang Moo Kyul. Problems arise when a perfect guy with a good background and prestigious education, Byun Jung In, gets in the way.
: Hong Suk Goo
Won Soo Yeon
: In Eun Ah
(Moon Geun-Young) is a young woman with the energy of the sun. She looks like her late mother, but her hot temper comes straight from her deadbeat father (Park Sang-Myeon). Her father always makes troubles as a failed businessman, but Mary also loves him the most. Because Mary can't afford to pay her college tuition fees, she temporarily stops attending school. Without having any special skills, Mary starts to work odd jobs. One day, Mary's father proposes that Mary marries a man named Jung-In to pay off their debts. When Mary hears of her father's plan she devise her own plan. Mary takes fake wedding pictures with her new friend Mu-Gyul (Jang Geun-Suk), whom she has just met over the last couple of days. She sends the pictures to her father's cellphone with the message that this is the man she loves and will marry. Unfortunately for Mary, her deadbeat father has already registered a marriage certificate on her behalf with Jung-In! Jung-In then proposes that Marry spend 100 days of marriage with both men and decide whom she wants to live with.
(Jang Geun-Suk) is the lead vocalist and guitarist for a rock band. He is chic and lives a carefree bohemian lifestyle. He doesn't talk much and only wants to make music. Mu-Gyul doesn't care about success. He also suffers trauma with his mother and, because of this, becomes tired of the women he dates and leaves them. Mu-Gyul is a bad guy to women. When it appears Mu-Gyul will never get married a once-in-a-lifetime opportunity comes about. He meets Mary, money becomes involved and a 100 days of marriage ensues. During this time, Mu-Gyul not knowing the meaning of family, surprisingly falls in love with Mary who is combative, loyal, and spunky. Mu-Gyul finds himself becoming a rival of Jung-In for Mary's love.
(Kim Jae-Wook) is the president of music company JI Entertainment producing a music drama. Jung-In was born into a wealthy family and has never lacked money. Jung-In is also good looking and has good manners. Because of this, Jung-In appears to be highly eligible bachelor for marriage. But, Jung-In also has a cold side - he doesn't like becoming too close to people. His weakest point is that he can never say no to his father. He enters into a 100 day fake marriage with Mary and soon falls in love with Mary. Jung-In also comes across Mu-Gyul who will help fulfill Jung-In's dream in the music world. Mu-Gyul will also become a rival for Jung-In over Marry. Then Seo-Jun enters the picture.
(Kim Hyo-Jin) is a sexy and sophisticated woman. She also comes from a rich family. Seo-Jun works as an actress, preferring to make movies rather than dramas. Seo-Jun broke up with Mu-Gyul about a year ago, but still occasionally attends his performances without his knowledge. She also has the same care-free spirit as Mu-Gyul. Seo-Jun then meets Mu-Gyul once again and makes a contract for a drama produced by Jung-In. Seo-Jun starts to develop feelings for Jung-In in a bizarre love triangle.