Maeng Sun-yi sacrificed her childhood and youth to taking care of her father, who started drinking heavily after her mother abandoned them when she was 10, and her two younger siblings. She even gave up her own education because she had to work hard to earn her siblings' tuitions. She is married to a guy named Ban Sung-moon, her five years junior, and has two daughters with him. Her life continues to present her with endless hardships but she just believes that that is "happiness". One day her husband falls in love with an attractive divorced woman and demands a divorce from Sun-yi.
Sun-yi's younger sister, Maeng Young-yi, is a successful career woman. She dates her first love Lee Jung-do, who is now married to another woman and who broke up with her for the sake of his career in the past.
Finally, Sun-yi's younger brother, Chul-soo, earns his doctorate degree in the United States and settles down there, completely ignoring his responsibility of taking care of his father.
Just to make things worse, Sun-yi is one day diagnosed with cancer, which to her is tantamount to a death sentence. After learning about her disease, her husband reflects on himself and shows her the genuine meaning of marital love.