Kim Taeyeon and Tiffany Hwang are strangers and somehow, they had to live together due to their fathers who are actually friends. Taeyeon thought of Tiffany as a spolit brat and thinks that things will not work well with each other. On the first day at night, there were lightning and thunder. Tiffany was really scared and screamed, making Taeyeon, who was not asleep, go to her room and comfort her. The next day, during a dinner with their fathers, Tiffany came home with her boyfriend and announced that Siwon had proposed to her. The couple left the house after a fight with Tiffany's father and there Taeyeon's mission starts. 

Kim Kibum and Lee Jinki are Tiffany's bodyguard. Kibum is usually seen calm and composed but he gets really jealous easily. Jinki is a really cheerful person but when he was asked to protect Tiffany Hwang, he had to keep his true personality aside and protect his boss. Not only the two had the same job, the two were even in love with each other but neither of them were brave enough to confess; especially Kibum since he thinks that Jinki was in love with Taeyeon instead.

Choi Siwon is Tiffany's boyfriend. He is a player from the start and does not actually love Tiffany. He only dated her because she had money and took advantage of her a lot of times. Since Tiffany was really in love with him, she was blind to see the bad side of him.

Will Taeyeon be able to complete her mission given by Mr Hwang? Will Jinki and Kibum be able to get together in the end? What will happen if Mr Hwang's plan failed? Will everything be like it used to be?