Won Geun-su

Having married young, when frustration with their lives make Choi Ban-du and Ma Jin-joo regret their marriage of 18 years, a strange occurrence has them traveling back in time to the day before they met and into their younger selves.

Every last Thursday of the month at an all-girls high school, the students of Class 2–5 cast their votes in a popularity poll. The results classify them into Grades A, B, C, D, and F. If they fall into Grade F, they become legitimate victims of school violence.