The best, most effective horror works by implication. H. P. Lovecraft knew this, as did the other practitioners of the so-called “weird story.” In many of these stories, the hero doesn’t have direct contact with the supernatural (ghosts or demons don’t leap out of the woodwork and tear them apart), but the characters find incontrovertible evidence that these monsters exist. And this evidence defies the laws of nature; its very existence is obscene and an abomination against reality (in Lovecraft’s Supernatural Horror in Literature, he explains quite astutely that the “weird” story only became possible once science had progressed to the point that universal laws of physics had been established; reality can only be obscenely violated once it’s been established). As for what is being implied, besides the existence of various monsters and nightmares, I think it is best summed up in this analysis of the work of British fantasy/horror/”weird” writer William Hope Hodgson, which I found on Wikipedia, and which is so well-written that I’m assuming it was plagiarized from another source: “Hodgson achieves a deep power of expression, which focuses on a sense not only of terror but of the ubiquity of potential terror, of the thinness of the invisible boundary between the world of normality and an underlying, unaccountable reality for which humans are not suited.”
Humans are a profoundly vulnerable species. Not only do we have weak, soft bodies (without claws, or horns, or venom) but we have the capacity to think, and with the capacity to think comes the capacity for madness and horror. There is a thin, transparent membrane of logic and scientific reason stretched tightly over the amorphous, monstrous body of magical thinking with which primitive man first encountered the world. This is where vengeful, super-powerful ghosts come into the picture; because, from a logical perspective, we know that the dead victim of an injustice is just that: dead; and he or she can no longer harm us. But the magical thinking that animated the human genius for most of our history tells us that the blood of criminality is rank, and that it rises up to heaven and calls out for vengeance. And so history becomes the proverbial nightmare from which Stephen Dedalus was trying to awaken. Every horror, ever violation of the codes of morality can come back to destroy us. To paraphrase William Faulkner, “The past isn’t dead; it isn’t even past; it is a pissed off Japanese albino from hell, with blood dripping from her eyes, come back to kill you in your bathtub.”
And so this is why Japanese ghosts don’t need to do anything. They take that which has been effaced by time and criminal deception, and they bring it back into the light of day. To steal a line from William Styron (who isn’t read anymore), who in turn stole it from John Milton: the Japanese ghost exists to render “darkness visible.” The ghost’s very presence constitutes an action, as it sets into motion the wheels of history and morality (albeit a brutal morality predicated on vengeance and terror). The ghost is the conscience of the human race, gone mad and out for blood. This ectoplasmic conscience holds up an appropriate mirror to the potential for psychotic violence and terror which exists in all of us.