It Follows (2014) is a modern indie horror classic where a mysterious, shape-shifting entity stalks its victims after sexual encounters. With its blend of psychological horror, supernatural menace, and haunting suburban atmosphere, it redefined the teen horror tradition and became one of the most acclaimed horror films of the 2010s.

A young woman is followed by a terrifying supernatural force after a sexual encounter with her new boyfriend.

Från IMDB:
A young woman is followed by an unknown supernatural force after a sexual encounter.