After being dumped by his girlfriend, Dae-hyun is approached by high-school tough girl Saet-byul who needs an adult to help her buy cigarettes, but she is rewarded with candy and a lecture instead. Thankful for his caring act, albeit somewhat sarcastically, she surprises him by giving him a kiss. They go their separate ways and do not see each other for a while. Three years later, Dae-hyun manages his family-owned convenience store but is repeatedly forced to work multiple shifts that deprives him from getting any sleep and he struggles to keep up with the daily operations of the store due to his fatigue. Although high school girls like to come in and take pictures with him, the store doesn't make a lot of money. In order to keep his business afloat, Dae-hyun's father urges him to hire a part-timer to help him out with the store. With Saet-byul being the only applicant, Dae-hyun reluctantly agrees to hire her on a probationary basis.