Park Jiyeon got played by 3 guys and she declared that were enough. So, she just being a friend with every guys. Till, she met Kris Wufan, a new guy who was older than her. Since, Kris was nice. She asked him to be her foster brother. 

But, after months 'acted' as fosters siblings. Jiyeon realized she actually in love with Kris but afraid on confessing cause afraid of lies.