Tie Up the Girl! (1978)

Original title: 少女を縛る!

A girl is sold to a brothel. She is destined to become a prostitute, but because she is still a child, she is made to work as a maid there. Because she grew up in the countryside, she is careless in everything she does, and is constantly mocked by the landlady and the prostitutes who work there. One day, the girl takes the undergarment she was ordered to wear and heads to the room of a prostitute's older sister. As soon as she opens the sliding door, she is shocked. There she finds her older sister tied up with rope and being tortured by a male customer. The girl instinctively shouts "Stop it!", but is shocked to see that the older sister does not seem to mind, but rather seems to enjoy it. Before long, the girl is unable to get the scene out of her head, and begins to secretly tie ropes around herself in her room...