Characters;

Choi Sunmi -- A new student at the university who's quite naive, childish and so on. Her grades are mostly average and she doesn't get into much sports. She's basically a klutz who'd rather sit in the library and read a couple of books rather than moving in general. On her first day in the universtity, she was surprised by her senior, Yong Junhyung who welcomed her into the university with a kiss. Flustered, Sunmi wishes never to find this guy again. But she does... and she even spends most of her classes with him. Sunmi finds herself also falling for Junhyung's friend who is most definitely not like him, Jang Hyunseung who is a complete gentleman unlike Junhyung.

Yong Junhyung -- A second year student who is walking trouble. He goes around breaking girls' hearts and whatnot. He skips a few classes and is a rebel that basically lives in the Principal's office. he swears he gets any girl he would like and even does bets with his classmates and friends on whether or not he will get the girl. He was asked by his friends to target Sunmi, which he did. But what is this-- he finds himself charmed by the girl's cuteness and cluelessness? This feeling is so new to him... how will he manage it? -- He later develops the nickname 'Nappeun Namja'  from Sunmi, meaning 'Bad Guy.'

Jang Hyunseung -- One of Junhyung's friends who dislike how Junhyung treats girls. He's a gentleman and respects every girl. He's sweet to most every girl and so when Sunmi finds herself falling for him, Hyunseung has second thoughts on whether to return the feelings or to turn her down. He wants to be a gentleman and not hurt her... but he doesn't want to pretend as well. Or maybe he'll find himself falling for the charming little girl, too? -- he gets called 'Cheonsa Oppa' at times by Sunmi, meaning 'Angel Oppa'

Choi Gina - Sunmi's elder sister who goes around job-hopping to try to keep her and Sunmi alive. She's a great support to Sunmi and is a willing shoulder to cry on. She's the only one Sunmi lives with ever since their parents had to leave without a word, flying off to America. She is very fond of Hyunseung and dislikes Junhyung from his head down to his toes.

B2ST -- The name of a group in which Junhyung and Hyunseung is a part of, along with Yang Yoseob, Son Dongwoon, Yoon Doojoon & Lee Kikwang. They're who Junhyung is always witha nd who he usually consults about his feelings, especially Kikwang.

Lee Sunkyu -- Also a new student i the university who is latter found as Sunmi's best friend and companion when it's at school.