Graduating from Waseda University in 1984, Kamanaka began working as an assistant director for documentaries at Group Gendai, Iwanami Productions, and other companies. She directed her first film in 1990 and between 1990 and 1995, worked and studied in Canada and the United States, first on a grant from Japan's Agency for Cultural Affairs. Returning to Japan, she worked as a freelance director for television and film. Her film, Hibakusha at the End of the World (also known as Radiation: A Slow Death), was the first of several she has made on the problems of nuclear radiation. It won several awards, including one from the Agency for Cultural Affairs for excellence in documentary. Her next film on nuclear issues, Rokkasho Rhapsody, covered the problems surrounding the Rokkasho Reprocessing Plant. Her most recent work, Ashes to Honey, about residents fighting the construction of a nuclear power plant in Yamaguchi Prefecture, opened in theaters only a month before the Fukushima Daiichi nuclear disaster. After the disaster, her work has garnered increased attention and she has been asked to present her work at numerous venues at home and abroad.