It takes a keen eye to spot them, but some of the holes are the size of children. Imagine how the parents must feel when their child disappears... and comes home looking like that. Assuming they can even walk or talk when they emerge, the psychological trauma alone will have reduced them to gibbering lunatics.
Or, what if the parents, in their own mad desire to enter their holes, bring the kids with them...
It doesn't really seem like the holes will admit anyone other than the intended occupant/victim very far, so thankfully this scenario is unlikely to be possible. Unless, of course, the parent forces the child to go in front of them, in which case there's no possible answer to the question that leads to pleasant dreams.
Some of the holes have it where the person has to bend their neck a little. Consider how they stretch enough that those whose hole was that of normal stance do get their necks bent at some point.
Only some holes seem to go all the way through. Assuming the holes keep people magically alive during their hole stay, then anybody with a blocked hole (such as Nakagaki, unless he was just at the point when his body would have to stretch) would end up spending eternitynote or until somebody dug them out stuck in one spot and alive. And, judging from the researcher near the end who comments on the fault on the other side of the mountain being much smaller than the entrance fault, this likely happened to most of the people who went in.
It's possible that, given the shapes of the exit holes, the other fault is still large enough to accommodate everybody. Let's hope this is the case, anyway.
Where is it stated that there needs a one-to-one correspondence between entrance holes and exits holes for everyone to get out? Maybe some of the tunnels run into each other...
Or maybe some split...
It could be the 2nd fault split some of the tunnels somewhere in the middle. The rest just keep on going, deeper and deeper...
It may just be the effect of shadows, but the spaghetti-men who emerge at the end appear much darker than those who entered... most likely as a result of having all their innards squashed until they burst.
In the dream, the holes serve as a means of punishment for "a horrible crime". It's possible that the holes exist because everyone at the site is guilty of doing something terrible.
Or, perhaps, the past-people are dicks, and just want to get their spiteful revenge on all the future people who have survived the collapse of their civilization.
Yet, how would they even know what future people would look like? Unless they can see into the future, or something was telling them to.
Possibly the modern victims of the holes are the reincarnations of the original criminals, and look the same as they did in their past lives.
The holes are angled slightly downward so people go in. As part of the silhouette, there's a big pointy piece of rock pointing at the crotch. It's like if someone turned a wooden horse into a slide.
What's so creepy about that?
You... don't find anything additionally unnerving about all the rest of the stuff happening while sliding down a big pointy wedge jammed up into your genitals?
Seems they thought op meant a wooden rocking horse, rather than the wooden horse. The wooden horse is a torture device that often injured the genitals. It was triangular in shape and the person was forced to sit on one pointed edge. Now, imagine that, but with rough stone instead of wood, and instead of sitting on it, the person's dragged across it.
They do keep their underwear on, so it's probably not that bad... relatively.
When you think about it, the best possible outcome of someone passing through Amigara Mountain would be their death when they came out on the other side. More likely, though, given the fact that whatever created the holes keeps them alive for months without food and water while they creep through, they're forced to go through the rest of their unnatural lives as the deformed creatures who exit the mountain. Assuming that they're still able to move at all, they probably won't be able to walk or to do much of anything other than lay on a hospital bed and writhe in wordless agony.