The Forest

Sarah and Jess are twins. Jess goes missing in a forest in Japan notorious for people killing themselves there. Sarah is certain her sister is still alive - twin sense - and determined to search the forest for her. She meets a feature writer named Aiden that had arranged to accompany a man named Michi who goes on hikes through the forest seeking people who might be lost in one sense of the other.

Sarah is repeatedly warned, and repeatedly dismisses, the notion that it's a bad idea for someone who is sad and hurting to enter these woods, because the spirits of the deceased will take effect on her. She has a lot of guilt with regards to her sister, and sure enough, starts hearing things, seeing things. The attempts at jump scares don't really work. Not sure why, other than the movie might telegraph them too much. Little too obvious something frightening is about to happen.

The film does a fairly good job most of the way through at keeping it ambiguous whether Sarah is really seeing what she thinks she is, or if her grief and worry is acting on her, or if there really are hostile spirits messing with her perception. This extends to her having doubts about Aiden, why he's there, what he's really after. And since we can't be certain if what we're seeing (which is what she's seeing) is real or not, we don't know if he can be trusted, either. And even if what she's seeing isn't real, it's presented in such a way that you see how it wears on her, stresses her out further, puts her in an even worse state of mind.