Rika Aoshima is the eldest daughter of an ordinary Japanese family in the mid-twentieth century. Though Rika is regarded by others as intelligent, athletic, and beautiful, her mother Yuriko believes that her daughter is an iguana; she frequently belittles Rika, and openly favors her youngest daughter Mami. Rika has internalized her mother's rejection and perceives herself as an iguana, and comes to believe that her true parents are iguanas in the Galápagos Islands.