Exhuma is a tale of shamanism and exorcizing trauma. The 1st half of the movie sets up an atmosphere for you to get curious about what's waiting for you ahead as you expected they may explain the course of the action but here you get disappointed cuz without explaining the movie went ahead on another dimension of Korean/Japnese flok shamanism from handling the ghost to fighting with an Oni real quick.

Screenwriter and Director Jang Jae-hyun specializes in horror movies, and as such, he often leaves the mystery to the audience's interpretation.

In the 2nd half of the movie, you understand what is happening presently and Oni's past but many things are unexplained like what is the relation b/w ML and Fl are they a couple (least likely) or siblings or just working partners or senior/junior? while watching the movie It wasn't clear what the relation b/w the MLs and the two females who were in the hospital while Hwa Rim was dealing with the Oni. According to MDL, Oh Gwang Shim [Hwa Rim's senior] and Park Ja Hye [Hwa Rim's junior] explain.
You may ask why you don't understand while watching? Is that your first supernatural/horror movie?

Nope, I have watched so many supernatural/horror/folk/exorcism movies whether it's Korean, Japanese, Thai, Indian, or Hollywood but they bother to explain or give you the hint so you can understand. But the story was narrated without giving any hints of explaining "it is what it is" and what was the relation b/w the 1st ghost we saw (Grandpa Park) and the Oni wasn't explained! ?

Now what I like and dislike about this movie;

Cinematography: No doubt it is excellent cinematography and gives you the experience to the fullest. The graphics were good too.

Acting: The acting of both actors was top notch and you can see them as a shaman. Kim Go-Eun acting as a shaman was excellent while performing the exhumation. Lee Do-hyun's acting was also impressive as a hot shaman. The acting was the main element of this movie that kept you in your seat. you connect with the characters despite no backstory.

Story: As I said before, the story leaves many loopholes where we as an audience find difficulty connecting the dots. The mystery and the suspense in the story were well presented. This movie didn't have any jumpscares or maybe I didn't find any.

Styling: One more thing that I like is the styling and costume of both leads. Kim Go-Eun's clothing style and her aura, she was the whole mood. Also, Lee Do-hyun's tattoos and hair bun stole the show.

In conclusion, to understand this movie I had so many questions, Like; what was the Park family's secret? Who was Gisune? (I have known about the Kitsune) the grave robber's angle? Who possessed Bong Gil? That was confusing but I thought the General Oni(demon) possessed him. What kind of creature was that snake (Nure-onna) that was killed after the ritual?

I had to do some research and find I am not the only one who was confused thanks to that Reddit explanation I got my answers. If you don’t know much about Korean/Japanese history/shamanism it will be difficult to understand as well.

Without knowing the explanation I gave this movie 6.8 out of 10 for excellent acting, cast, and cinematography. Also, I can't deny the fact that this movie is Overhyped because of the cast. If you had to find an explanation outside of the movie then what to say?