Surely A Happy Ending summary: Yeon-Woo's husband died the day they ended their sham marriage. Yeon-Woo, who is swept in sorrow, is given a chance to return 100 days back in time! As she struggles to prevent the death of her husband Seon-Jae, their ‘real' marriage has only just begun. This is the story of a late budding romance, faced with danger and a life at stake.