SPOILERS AHEAD...
I saw this tonight. And it def has to do with grudge series. The mom felt that same house from the 1st felt off. If she had stayed in Japan it would have been boring. I liked she took the story back to the states.
And changing it up with the 3 from the 1st murder makes sense. 1st family to die of it in that house. So why would we see the girl and boy from 1st one?
And the back and forth make sense as she goes through the files. It all comes together nicely.
Ending maybe predictable. 1st jump scare was a surprise. After that a few you knew coming but still scary I love horror. Seen everything from the 20s was on up..so very picky.