24-year-old college student Shang Ming (Kim Rae Won) received an incredible order from his grandfather: he must marry 16-year-old middle school student Bao En (Moon Geun Young). It is said that this is a promise made by the previous generation, but these two people who are eight years apart and from different worlds inexplicably stepped into the marriage hall. This marriage that came too early made Bao En very uncomfortable. She originally liked the boy on the baseball team, and she secretly ran out to date him after getting married. Shang Ming is still a responsible man. He wants to take good care of his young wife no matter what. Until he went to Bao En School as an intern teacher, embarrassing things came one after another! He couldn't let others know that he had a 16-year-old wife, and he had to resist the pursuit of young female teachers. His marriage with Bao En was even more uncertain.