Kairo addresses an intriguing issue that no other ghost story does...

that I know of anyway. And that is the issue of vacant space in the afterlife, the "other world", heaven/hell, whatever you want to call it.

Think about it. For the purpose of the topic, let us assume that there is in fact an afterlife. It is the place we go to after we die on Earth, our eternal second home after our brief (relative to eternity) first life.

But would that place not eventually become full? Think about the entire history of mankind, from our primitive sabre-tooth tiger hunting beginnings to our modern age [insert current year] as well as the future ahead of us (assuming our lack of action climate change doesn't wipe us out prematurely). There are two constants in life: death and taxes. How many people have died since the beginning of time, and will continue to die in the future?

According to some sources, about 50 million people die each year (and even more born). That's almost 150,000 deaths a day. All of these millions of dead souls will depart for the other world. I hope the spirit world government has good land management and public infrastructure under control. Otherwise, it will end up like Kairo: the ghosts will "leak" back onto Earth, "deported" back.

As much as I like horror movies, "haunted house" is one concept that I'm increasingly getting too old for and cannot accept. My suspension of disbelief is at its limits. Think about this on a more micro level. Suppose there is a house owned by a husband and wife and the wife is murdered for a perceived slight by her husband in a drunken rage and then her corpse hidden in the basement. The general requirement for a haunted house is someone who is killed (often in shock or emotional at the time of the incident or violently killed) then becomes a ghost with unfinished business in that house.

What if another unjust killing happens again in that house in an unrelated incident? Now you have two ghosts haunting the same house. Ghosts also often kill their human victims in violent or shocking ways. Do their victims not also have the "right" to become ghosts too? Now there are four ghosts. This isn't scary anymore. Now it's absurd. Ridiculous. Unrealistic.

Anyway, that's just one of the many issues that this movie, one of the best movies of all time (horror or not) mind you, raises. At this rate, it will remain one of the best horrors in the foreseeable future (if the jump scares with ear-shattering sound effects of today's movies are of any indication). Shout outs to "It Follows" though for being one of the few movies since Kairo to conjure up the feeling of pure dread.