When she was six, her father went to the Middle East for a manual labor job, leaving the rest of the family to move into her grandfather's house in Geumsan County, South Chungcheong Province, where she ended up spending her childhood.

Upon entering high school, she joined a literature club, the Cheong-un Literary Society, and dabbled in writing poetry.

After graduating from university, Kim Sum worked as a proofreader for a newspaper outside of Seoul, and then as an editor for a publishing house for many years.

Known for her "elaborate descriptions and aesthetic style" and "vivid allegories",[3] Kim Sum has been a prolific writer since her debut, publishing numerous short story collections and novels.

While One Left (한명) tells the story of Korean comfort women who were sexually abused by Imperial Japanese soldiers, L's Sneakers (L의 운동화) retells the story of student activist Lee Han-yeol, whose injuries and later death strongly influenced the June Democratic Struggle of 1987.