The hole appears after a destructive typhoon hits the small town and the city nearby. As villagers rummage through the storm's wreckage, they notice that a shrine that has been in the town for as long as they can remember, perhaps even for centuries, has been destroyed. When they are...
searching for the place where the new shrine should be erected in place of the old one, someone discovers a hole.
The moment that the hole is discovered cannot be considered the climax of the story, nor is it very exciting. Instead, someone simply notices it, and people start to talk about what to do with it. This part of the story, the catalyst for the rest of what happens, reads:
Just then one of them raised his voice. "Hey what in the world is this hole?"
Where they had all gathered there was a hole about a meter in diameter. They peered in, but it was so dark nothing could be seen. However, it gave one the feeling that it was so deep it went clear through to the center of the earth.
The relationship between the shrine and the hole (and the shrine's destruction and the appearance of the hole) is never concretely established; that is, we do not know for sure that the hole appears because the shrine is destroyed. However, it is useful to think about the possible connections between the disappearance or destruction of the shrine, something that represents a certain history as it is tied to a certain place, and the appearance of the hole, which seems to represent uncertainty, disposal without consequences, and forgetting.
The hole is never completely understood by anyone throughout the story. The media, scientists, and eventually industrialists all have various theories about the hole and ideas about how it can be used. We, as the readers, are never told exactly how or why the hole appears, nor what its purpose is. However, we do get a feeling for the consequences of using the hole as it has been used (for example, disposing of nuclear waste and attempting to erase the past by throwing in diaries, evidence of affairs, or crimes committed) when, at the end of the story, the words "He-y, come on ou-t!" are finally, after awhile (though we're not sure how long exactly) echoed back, and the pebble thrown in right after the hole was found appears again. It seems that what has been put into the hole without thought or fear or knowledge of consequence is returning, and though the words and the pebble might not harm anyone, the nuclear waste and secrets from the past will inevitably do harm.