Angel Guts: Red Classroom (1979)

When Muraki, a porn producer, watches a blue film depicting a gang rape in a school, he becomes obsessed with the lead actress. Quite by chance, whilst looking to reserve a location for a shoot, he happens to encounter her at a love hotel where she works as a receptionist. Her name is Nami and she reluctantly agrees to speak with him, and confesses that it was her in the film. Then, Muraki tells Nami that he wants to help her...