I think ambiguity is a good word to use. I think it helps to avoid making presumptions, but I rather doubt KK would agree that there are no definitive statement of his in the films.
I would agree, having only seen a couple of his films so far (Pulse, Bright Future and Doppleganger), that ambiguity seems a perfect word to describe at least these films. There is never really an explanation as to how events are triggered off and what the characters are exactly feeling that is making them do what they do. I actually prefer Bright Future and Doppleganger over Pulse really only for the reason that I think when a superficially 'genre' piece is being made that you need to be very clear about the rules of the world you are creating, even if you do not explicitly tell them to the audience.
Spoilers for original and remake of Pulse:
Having said that, I like Pulse very much and was very interested in watching the remake to see how they tackled the material. Even just the remake's cover forewarned of a much more literal interpretation and Horror with a capital 'H'!
While I much prefer the original film, I find that watching a remake and thinking about the things it gets right or wrong (only in my opinion, of course) can be a worthwhile exercise in helping me to crystallise my feelings about the film, especially when the original is so ambiguous!
Some of the changes in the remake helped to illuminate the original's themes. For example I would argue that the original film is not exactly a 'horror' in the classical sense of monsters and ghouls. The closest to an explanation we come in the original (which seems more just speculation about the nature of the phenomenon and which brought to my mind the discussion of the cafe customers in The Birds) is of how the dead started spilling over into the world of the living through overcrowding and that they are not evil in intent but more just lost souls.
Since I'm a nerd I immediately thought of that Dawn of the Dead line "when there's no more room in hell, the dead will walk the earth", only with ghosts rather than zombies! I also got the impression that the idea of the world being overcrowded due to the dead coming through in massive numbers, creating more and more 'forbidden rooms' in abandoned industrial areas, while the indiginous population either assimilates or disappears in other ways, was meant to be a quite funny comment on immigration and overcrowding of a relatively small island country. That the film ends with the remaining characters out in the middle of the ocean, trying to find a new home, seems to add weight to that interpretation.
That theme is not really applicable to the US, since the one thing there seems to be an abundance of is space! So the characters are not forced out of the country but instead just out of the cities and into areas where there is no signal range (which might be just as bad for city dwellers!) to continue the war (and it is a war in the remake) in a fashion that recalls the end of The Terminator.
There might also be a bit of irony at work there as usually characters in horror films are always finding that they cannot get a signal on their mobile phones (usually the first sign something is going to go horribly wrong or they are about to get bloodily murdered!), so the change to having to lose the phone signal to be safe was quite nice! Though this does point out another (cultural?) difference in the treatment of technology. In the Japanese film the computer itself is not really the cause of the disaster, its role in the dissemination of the ghosts is just a continuation of its role as a conduit.
There is a theme of physical separation but mental connection but it seems less to do with technology being evil but that it can give full access to ideas we had never considered before, both good and bad. After all Japan is hardly unused to a high suicide rate but more connectivity allows these kind of ideas to spread further than they ordinarily might have (there are some parallels with the Ring there). Similarly in Britain recently there has been much made of a spate of young people all killing themselves in such high numbers in so small an area to not seem suspiciously connected
. I think in the Kurosawa film the ghosts are another expression of this spread of ideas, as if contact with the ghosts leads to a feeling of futility, of uselessness and loneliness that overpowers the usual ability to carry on with life. It does not seem to be really intended by the ghosts to cause these feelings - I would think of it more like being in the presence of a really
depressing person! No matter how much you try to remain upbeat eventually the negative energy rubs off! It does not mean there should not still be sympathy for the person who is depressed though!
It makes the image of someone literally becoming a shadow or becoming ash and blowing away sadly beautiful, with the emphasis on those left behind who cannot help or prevent their friends leaving them or comprehend their leaving. The difference in Michi's reaction to the loss of her friends, especially Junko, and her eventual acceptance of Ryosuke's leaving is beautifully done to show she has come to terms in some way with passing on.
I didn't really feel that from the American remake, which never really gets past the idea that death is something to wage war against and uses the shadow and ash idea in a similar way to Stephen Laws' book Darkfall
The major change in the remake is that the ghosts really are threats (less sad apparitions and more 'Come To Daddy' influenced screamers) and there is more of a concrete explanation given for their sudden appearance in that they were alerted to the presence of the real world by the search for new exploitable frequency wave bands. There is more of a reduction from the original in emphasising the blandly carefree nature of the kids in the film who then have their 'joie de vivre' sucked out of them in a disturbingly literal manner! As if they've never experienced a depressing moment in their lives before they have contact with ghosts!
One of the more strange changes is to the 'forbidden rooms' covered in tape - in the original they were there to signify no go areas now inhabited by ghosts (a new twist on the abandoned haunted house?). In the remake the ghouls are everywhere and instead it is the living people barricading themselves into their red rooms in terror.
I was left with a feeling of (albeit apocalyptic) hope from the Japanese film: things will never be as they were but there is still some connection there and possibility of co-existence with the ghosts, even if there is always the threat that they will overwhelm the living world as they did the dead - at least until they find a way to make people immortal! I love the way Koji Yakusho is used as a recognisable reassuring face, like throwing in Sean Connery in a cameo at the end of Robin Hood: Prince of Thieves! (Sorry, I tried to think of a better example!)
The remake is strangely even bleaker: we brought this on ourselves by our technological society meddling with nature, the ghostly world is horrific and unforgiving and all that is left is trying to wage some kind of future war for some kind of control of the living world. If either film were to cause legitimate depression it may be this one!
One other thing I love about Japanese horror films - no matter how dark, bleak or horrific things get they all seem to end with a kawaii upbeat rock/pop tune! It would seem as incongruous as the Spice Girls doing the end credits song for the latest Hostel film but somehow it works!