DUFF: - adj.  

Stands for designated ugly fat friend. That one friend who is seemingly less attractive in which a woman brings to make herself look better by comparison.

Cheon Haneul is the type of girl who is seems to be "blessed"  with the power to get every guy make a double take at the sight of her presence.

"Smart, pretty, charming" are the words that are often used to describe her and not to mention her kind hearted personality it would seem that Haera is the full ideal package right? 

 So why is she the only one out of her friends who is still single and least approached? 

Not that it mattered to her anyway, at least until after an interview with school newsreporter Kim Mingyu, who brings the topic to light by calling Haneul "the school's unexpected Duff." 

Taken a back by the comment and re-evaluating her actual status,

Haneul can't help herself from thinking.... 

What makes her the DUFF one out? 

or rather WHY?