Yeon-Woo’s husband Seon-jae died the day they ended their arrange marriage. Yeon-Woo, who’s swept in sorrow and grieve, was given a second chance to return back 100 days in time! As she struggles to prevent the death of her husband, their ‘real’ marriage has only just begun. This is the story of a late budding romance, faced with danger and life at stake. “This time, I’ll make sure that we Must Have A Happy Ending!”