The Key (1974)
aka Kagi
Genre: Drama | Pinku | Erotic
Country: Japan | Director: Tatsumi Kumashiro
Language: Japanese | Subtitles: English (Optional, embedded in Mkv file)
Aspect ratio: Cinemascope 2.35:1 | Length: 90mn
Dvdrip H264 Mkv – 846×372 – 23.976fps – 1.27gb
https://www.imdb.com/title/tt0071710/
An elderly college professor wants to bring the joys of sex to his wife. He bribes his son in law to shag her because it makes him jealous and he can perform better. He keeps a journal of his fantasies in a locked cupboard, hence the title, and hopes that his wife will find the key and read it.
No relation to a Tinto Brass film with the same title . . . .