Kwon Yuri.

• an audacious young woman
• willing to do anything to get what she wants
• loves money
• Kwon Yuri, a practiced conwoman,  has just been conned herself, by her formerly close con partner, Park Yoomi. Yoomi has taken all their money and ran away; an old habit of hers, Yuri believes. She's completely broke and decides to find her new con target: Park Yoochun. She's heard from Yoomi all about her dear older brother, Yoochun and she decides to have Yoomi pay by living off of Park Yoochun for awhile.

Park Yoochun.

• a cordial, mature young man
• the ideal son-in-law and husband
• deals with mild depression after loss of family
• The parents of Park Yoochun and Park Yoomi have passed away on Yoochun's 18th birthday. That year, Yoochun's dear younger sister, at age 15, the only family he had left, disappeared, nowhere to be found. So from age 18, he's lived alone. He is always missing his sister, but moves on with his life, with the help of his friends. But one day, eight years later, he finds a pretty woman on his doorsteps, claiming to be his younger sister. At first, Yoochun is doubtful of her alleged identity but because of his wishful thinking and of the fact that she knows so much about his sister, he decides to believe her and take her in.

Im Yoona.

• a lively and kind young woman
• Yoochun's first love and close friend
• persistent in whatever she does
• Im Yoona has harbored a crush on Yoochun ever since she was sixteen years old, when she first met him. Having a three-year age difference with Yoochun, Yoona belatedly discovers that he, at one point, liked her too. She is stuck in the friend zone, wallowing in her bad timing, but waits for the "right time". She is joyful when Yuri comes as Yoochun's alleged sister, hoping "Yoomi" is the key to making her and Yoochun a couple.

Jung Yunho.

• a mischievous, charismatic  young man
• Yoochun's best friend
• doesn't listen to anyone but himself
• Jung Yunho is the last, but not least member of the close "Y trio." The most mischievous of the group, he can't stay still and is always getting into trouble. When Yuri arrives, he's attracted to her instantly and his trips to Yoochun's house become more frequent. Perhaps he even falls in love, the word he never believed in before Yuri came into his life.