Nadie conoce a nadie (1999)

In Nadie conoce a nadie (AKA Nobody Knows Anybody), an aspiring novelist in crisis earns a living by filling out crossword puzzles. A mysterious message on his answering machine instructs him to insert a certain word into one of the puzzles he is creating, dragging him into a vortex of riddles, dangers, and confusion. He soon finds himself involved in a real-life version of a video game on the streets of the city, with potentially devastating consequences for everyone.
At the seventy-fifth minute, we see Natalia Verbeke naked, bent over a guy as she rides him on a bed, in a sex scene in a concrete room. Natalia shows the profile of her breasts and butt. She rides the guy for a while, then gets up and leaves the room.