Mark and Nayeon used to in a relationship together when they were young during their high school life. But they broke up after Nayeon's homeroom teacher found out about their relationship issue. 6 years laters, what happen between them when they met each other again as his ex-girlfriend is medical student who takes a responsibility to take care of his father sickness?  ''I never expected to meet him again even though I try to erase him out from my memory'' - Im Nayeon