In the Realm of the Senses (1976)
In the Realm of the Senses (French: L’Empire des sens} is a 1976 French-Japanese art film directed by Nagisa Oshima. It is a fictionalised and sexually explicit treatment of an incident from 1930s Japan, that of Sada Abe. It generated great controversy during its release; while intended for mainstream wide release, it contains scenes of unsimulated sexual activity between the actors (Tatsuya Fuji and Eiko Matsuda, among others).
More at Wikipedia.