The Japanese Tie Up (1980)

Original title: 激撮！日本の緊縛

Separated from her lover Kenji after he is sent off to war, Sanae is raped by general Takada and gives birth to a girl, Junko, who grows up to become a prostitute. One day, Kenji accidentally meets Junko and confuses her with Sanae, prompting Junko to tell him of her mother's fate. They make love, leaving Junko pregnant with his child - Hiroko, who goes on to have a chance encounter with Takada at a hostess club...