Pulse

Pulse is a 2001 Japanese horror film directed by Kiyoshi Kurosawa. It's a type of ghost story, and I like these much better than the splatter- and gore and torture-filled horrors that seem to have become more popular. I have to say, though, that I didn't experience this as a horror movie. It was one of the saddest films I've ever seen, a picture of loneliness and isolation. You can watch it on Tubi TV.

trailer:

There was an American remake, which I haven't seen, in 2006.

Slant Magazine opens its review with this:

During a Kiyoshi Kurosawa film, one sits in anticipation of the horrors lingering just outside the frame, and there's a profound sense of unease in those moments of stillness and indecision. Existential dread is an easy catchphrase to toss around, and has become the label for many a psychological terror tale dabbling in the fragility of the human condition. Kurosawa's movies have a genuinely unnerving effect on the viewer because they deal with the kind of loneliness that exists in an overcrowded world.

Moria says it "offer is a great deal of haunted atmosphere, which almost compensates for total confusion about what is happening." Empire Online gives it 3 out of 5 stars and says, "While not exactly reaching Ring-levels of terror, it’s certainly one for connoisseurs of the weird." DVD Talk says, "this is the kind of film that symbolizes what's so special about the sudden emergence of Asian horror. With very little gore and an overabundance of atmosphere, this is a strikingly thoughtful, Highly Recommended take on humans and their place in the universe." Horror News says, "if you are into the ghostly side of J – horror really like RINGU and JU – ON and still have not seen PULSE it is definitely worth your money and time". It has a 73% critics score at Rotten Tomatoes.