Sansan, the protagonist of Eighth Moon, tells the story of her life from age four through seventeen. Focusing on her family and her school friends, she also reveals much about life in Communist China. She is a candid and forthright narrator as she reveals her shortcomings, her aspirations, her fears, and her deep love for her family and her land.
"Mama" is Sansan's guardian. When her sister and brother-in-law leave for a trip to the United States, Mama agrees to keep their year-old daughter. When this trip stretches to seventeen years, she continues to raise the child. Mama is not an appealing character. She is a short, dumpy woman who is suffering from some glandular disease which causes her body to swell up. She also has a terrible temper. She sometimes beats and berates Sansan. She tries to keep Sansan in China by telling her that she belongs to them, that since she and her family raised her, she owes it to them to stay and care for them in their old age.
"Papa" is another conflicting character. Sansan admits that her first memory is of Papa caring for her during an illness. It is a very touching portrait of the man who later brings her a small present every day when he returns from work. After the revolution when food and money becomes scarce, this special treatment stops. Papa supports the revolution and favors the reforms, but he continues to like his comforts.
Grandmother is a matriarch of the family. She lives in the basement of the house surrounded by trunks containing the artifacts of her former life, where she has hidden her treasures away from her daughter. She is symbolic of the old ways. Her feet were bound and she has to pull herself along on a rope to get out of bed. She is strong and tells her granddaughter the truth about her family. She also helps Sansan leave China.
The other main character in the book is Sansan's "real" mother who writes to her from America and eventually contrives to get her to Taiwan by feigning sickness. Although it seems incongruous that she should have left this young girl behind for seventeen years, it is apparent that she really does love Sansan.