No Filter: These Actors Were Really Getting Intimate On Film!
Fruits of Passion (1981)

This 1981 film by Shūji Terayama was based on a novel by Pauline Réage, Retour à Roissy. Fruits of Passion contains acts of unsimulated fellatio. In the film, a character named O, played by actress Isabelle Illiers, is placed in a Chinese brothel to complete her “training.”
Once inside the brothel, our main character is subjected to various humiliating and sensual experiences in order to exhibit her obedience. There is also a subplot that features some interesting rhetoric about rebellion and resentment towards Europeans. Reviews for the film are not great.