PULSE (2001, a.k.a. Kairo) isn't particularly scary but it does a pretty good job of creating a sense of impending doom. The film is another in the long string of arguments in favor of evoking tension and mood rather than over explaining or clobbering the audience with exposition. Things happen slowly in this movie. That's not necessarily a bad thing but the payoff isn't a big one in terms of scares. Instead the film aims for creating a sense of doom and gloom that hangs rather substantially over the entire second half. It's not quite enough but it is interesting and at times chilling to watch. We know that something is happening in Tokyo, something that involves ghosts crossing over into our world and sucking unsuspecting victims into its own but we are never really told what is literally going on. It's all speculation on the part of the main characters.
I don't suppose one really needs a true explanation though and it does help that many of the scenes are visually stark and creepy in a way that has more to do with color desaturation and tonal restraint than with giving away everything and the kitchen sink.
The American remake (2006, also called PULSE) has some inventive visual effects but goes too far in the other direction. Everything is literalized until we just don't care anymore about anything or anyone.
If the original is a tease and we're just not sure we are getting enough out of the seduction then the remake is someone who sleeps with you on the first date and you're sorry afterward that you did it. I don't strongly recommend the original but it does have its moments. The remake deserves a pass. It's the kind of movie you walk out on even though you wasted 11 bucks.
http://www.spout.com/films/192610/default.aspx
http://www.spout.com/films/260502/default.aspx