There's a terrific book (in English) called "Broken Silence: Voices of Japanese Feminism" that is a series of interviews with prominent Japanese feminists about their personal, academic and/or activist roles in feminism. The interviewer and translator is Sandra Buckley. While it doesn't specifically address manga or anime (and it's about 15 years old, oh crap, I'm so old!) it does give a really good overview of developments and the foundation of modern feminism in Japan.