After 20 years of divorce, the ex-couple reunited for the first time in a long time at their beloved son's graduation ceremony, but they still don't get along... They started a big fight in front of their son, despite it being a happy day. They swore they would never see each other again, but when their son returned from his graduation trip, he suddenly told them that he was getting married. Just when they were feeling relieved about their son's future after he passed the bar exam, he said he would help out at his fiance's inn. In order to stop their son from getting married at all costs, the ex-couple, who had been on bad terms with each other, decided to temporarily join forces...