Choi Dae Hyun runs into a group of female high school students, including Jung Saet Byeol. The girls look like troublemakers. Jung Saet Byeol asks Choi Dae Hyun to do an errand for them, which is to buy cigarettes from a convenience store. Choi Dae Hyun buys the cigarettes for them and Jung Saet Byeol gets his cellphone number, but he never gets a call from her.

4 years later, Choi Dae Hyun is now 33 years old. He runs a small convenience store after he quit his job at a large company. He is looking for a part-time worker to work the night shift at his convenience store. Jung Saet Byeol comes to his store and she soon starts to work there. She is not a troublemaker anymore. Jung Saet Byeol is now a university student and guided by her strong morals.