Kim Sejin, she’s the only daughter of the popular electronics brand, LG Technologies. Instead of actually helping in the busines, she decided to study interior design and was succesful. She was working for a firm and she gained popularity because of her talent. Sejin is known for her bubbly and teasing personality. She lives to annoy the hell out of her bestfriend-slash-fiance, Lay. She is friendly and approachable, but Sejin is a skilled master when it comes to masking her feelings.

Zhang Yixing or Lay, he came from a pure Chinese family that owns a number of hotels in South Korea. In contrast to his best friend’s sunny and outgoing personality, Lay is very passive and stoic. He might not show it but he really cares for the people around him. He’s hard to read but most of the time his girlfriend or Sejin can understand him. Lay has always been praised for his being progressive when it comes to managing their family’s business. And he tends to dote on his fiance a lot, because Sejin tends to be clumsy.

Kim Jongin or Kai, his family owns Samsung Electronics. Kai is outgoing and very playful(flirty). But despite that, he has an “iron grip” when it comes to business and his work. He changes when something has gone wrong, he usually loses his cool when he gets annoyed. His friends call him “stone hearted” because Kai doesn’t fall for a person easily.

Lee Heejin, she has been dating Lay ever since they graduated from the university. Heejin’s a medical intern at Gangnam General Hospital. Heejing, despite the situation Lay is in now, she manages to get along well with Sejin and is good friends with her. Sejin never annoyed her, in fact she liked Sejin. Heejin’s a little reserved and usually quiet but generally she’s okay once you get to know her.

Luhan or Lulu to Sejin, he is Sejin’s older cousin and the one currently managing LG. He’s the cousin with the baby face and a granny’s temper. Luhan is a spoiler, he lets Sejin do whatever she wants but once he loses it, even Sejin runs away.  A lot of females approach him but he turns them down. Luhan is good friends with Lay as well as Heejin and he is the only person who knows about Sejin’s secret.

So, will this work?

Two bestfriends agreeing to get engaged to each other for a year just to please their parents and prevent them from being cut off. After the 365 days, their shares would be passed to them and they would call their union quits. Something as simple as that, would there be no complications?

But, what if feelings form and problems appear?

What if the deal that they made will be the main cause of their problems?

And what if Sejin realizes that her secret isn’t a secret anymore?

Will Lay be willing to give his bestfriend to another guy?