Kamurai
Really good watch, could watch again, and can recommend (at least for the sexually open minded.)
This movie focuses less on young rampant sex and more of the decline that people sometimes get as they get older and want to be more adventurous without destroying their relationships. It also doesn't treat it as ridiculous a thing, while still openly admitting that it is something foreign and strange.
The movie does a great job of leading the audience (alongside the main character couple) into this strange new world, not of debauchery, but love and connection. Given that the premise of the movie is them getting together, it's not a spoiler, but this is a romantic comedy for couples, basically.
There is plenty funny to this movie, but...