Bae Suzy is a girl in her first year of high-school. Being the type to put others before herself, she hopes to make lots of new friends.  The boy whom is the centre of attention at her school is Kim Myungsoo. He is extremely popular, and friendly too, and people follow him around without hesitation. That's why Suzy hates him in the beginning. 

However, like all the other girls, it isn't long before she falls in love with him. But Myungsoo isn't over his dead girlfriend yet. Her name was Jung Krystal. She passed away a year ago, but her smile and everything he loved about her still haunted him. 

It's only now that Myungsoo gets told that Krystal was cheating on him at the time of her death... And that death wasn't an accident... She had been murdered by that boy who she had an affair with...

As a result, Myungsoo chooses not to trust people except his best friend, Park Chanyeol, but he still puts on a fake breathtaking smile for everyone...