Call of the Pistil (1971)

The directorial debut of Masaru Konuma, penned by Keiichi Ozawa using the pseudonym "Fuyuhiko Hagi". Masako is a journalist, and she is raped while researching a story. The rape causes her to develop amnesia, so her brother devises a novel way to get her memory back -- he has her boyfriend rape her again. It doesn't work, so the brother and boyfriend do more research, discovering that Masako was raped by an African-American soldier. As might be expected, they then hire a black GI to rape the poor girl yet a third time...