Song Mino, the worst boyfriend you could ever have is Son Areum's childhood friend, best friend. Never have they ever thought about one another romantically.... He was nice but mean to her at the same time. They were always like that but the troublemaker decides to show a different side of himself, just for her. He rids of his horrible dating style, his "I'm just being brotherly" excuses in front of his friends and most of all, he goes to school just so she would stop worrying about him. 

Koo Junhoe, the most blunt and sassy guy you'll ever come across but shows an innocent side of him. He's never dated a girl in his life but this girl, Son Areum has gotten under his skin and so he decides to get under hers too. But things didn't turn out the way he wanted to. She ends up disliking his antics and even worse, Mino was always in the way. He was determined to make her fall for him, just Koo Junhoe, not just the sassy, class president he showed out of his insecurity.  

Son Areum (OC), the most unfortunate person of the year... Feeling uncomfortable about the idea of dating, she actually lands herself in all sorts of problems between Mino, Junhoe and others in her last semester of high school. And also, she discovers Mino's longheld secret. Though they told each other everything. In a turn of events, she and Junhoe gets dragged into Mino's unintentional mess, driving the three into an even more complex relationship.