She heard that message in the behavior of her parents: His works include Justine, Juliette, and Days of Sodomy.
De Sade spent about 32 years of his life in insane asylums for his scandalous writing, numerous sexual assaults, and poisoning several women with the Spanish fly right before he had anal sex with them.
The Connection Between Sexual Pain and Pleasure
Ideas for inflicting pain during sex [Painful Sex] : sex
Use of Pain in Sex
The Pleasure of Pain
Sadomasochism - Wikipedia
It is an internal space where sensation is leader and I have long wondered what begets what, if it is actually the intensity of the pain that arouses the pleasure or the other way around.