A small shrine was there before the hole appeared, and no one knew how long it had been there.
At the beginning of the story we are told that a tsunami has swept through the countryside, leaving no village unaffected.
A little distance from the village and near the mountains, a small shrine had been swept away by a landslide.
When people talk of the shrine, no one seems to know who built it or when. They just say “it must have been here since an awfully long time ago.”
Even though the shrine has been destroyed, the people decide to rebuild it. When rebuilding it they notice a hole a meter wide. The hole seems to have no bottom, so they just randomly begin throwing things into it. They ignore the warnings of an old man who told them they are going to be cursed.
Eventually, everything that goes into the hole comes out. The story serves as a modern fable of environmentalism. We need to be careful what we do to the world, because we don’t really understand the effects of our actions or the damage we might cause with our foolishness. The people of this village learned that the hard way.