Irony is created when what we expect to happen is different from what actually happens. When the story opens, we learn that a typhoon has created a landslide that swept away a small shrine. Where the shrine used to be, villagers find a significantly sized hole in the ground. It seems as though the hole has no bottom and goes "clear through to the center of the earth." Evidently, whoever built that shrine an "awfully long time ago" felt that the hole was something to be safeguarded, something deserving of divine protection. When they did not understand the hole, they protected it and left it alone. Perhaps they viewed the hole as a vulnerability in the earth and, in an attempt to shield or secure the earth, they covered up the hole with something designed to keep it safe.

One would expect, then, that those people who find the hole—the descendants of the community that built the shrine—would do the same thing considering that their ancestors' actions seem to have prevented any harm. One person does suggest rebuilding the shrine "just as it was over the hole." However, people cannot agree on what to do and they end up using the hole as an all-purpose dump. They exploit the hole, first by trading it to a concessionaire who promises to build them a better shrine with a meeting hall closer to the village. Without knowing where the hole goes or what could happen, people begin dumping nuclear waste and all manner of other things into it. We would not expect this, given they have no idea what the consequences would be. This irony shows how humanity has changed: we used to revere and protect things we did not understand, and now we exploit them or use them for personal gain.

In the end of the story, the implication is that everything humankind wanted to make disappear by throwing it down the hole is now falling out of the sky. This is ironic because everything humanity wanted to get rid of or forget about is about to be, quite literally, thrown back in their faces.

The story tells us that if something seems too good to be true, it probably isn't true. All of the people of the world assumed that they had an easy answer for all of the waste, secrets, and other objects that mankind simply wanted to go away forever. No one ever thought to question the scientific or existential implication of a seemingly bottomless hole just appearing out of nowhere. In a sense, it can be called just deserts for the entire human race.

Another aspect of irony in the short story lies within the fact that everybody who dumps things into the hole feels a selfish sense of relief in doing so, only to eventually have their worst fears realized. Toward the end of the story, Shinichi Hoshi writes that "[t]he hole gave peace of mind to the dwellers of the city," going on to detail some of the things that are disposed of within it:

Young girls whose betrothals had been arranged discarded old diaries in the hole. There were also those who were inaugurating new love affairs and threw into the hole old photographs of themselves taken with former sweethearts. The police felt comforted as they used the hole to get rid of accumulations of expertly done counterfeit bills. Criminals breathed easier after throwing material evidence into the hole.

Each person, organization, even government agency believes they have unburdened themselves by "getting rid" of their undesirable matter in a way which will not harm the world but particuarly themselves. However, the twist at the end of the story, when a construction worker atop a high building hears a voice say, "He-y, come on ou-t!" and then fails to notice a small pebble falling past because he "was gazing in idle reverie at the city's skyline growing ever more beautiful," reveals the irony that our selfish attempts to unburden ourselves without repercussion will only burden others or return to burden us tenfold. Eventually the things that were discarded by all of the people will return for everyone to deal with. Diaries will no longer be private, counterfeit bills will spread freely, material evidence will be out for all to see, nuclear waste will rain from the sky. Nothing ever truly goes away; if we try to make something go away, it will only come back and cause even more trouble than it did before.

The story is ironic because the people believe they have found an easy solution for all of the terrible and dangerous waste they have created, and yet they don't realize that they're basically just throwing it on their own heads. When they discover the hole seemingly has no bottom, it seems like a great idea to just dispose of unwanted things into the hole where they can't bother anyone. This is a bit like sweeping dirt under the rug, its not getting rid of it, just hiding it. The scientists who are throwing dangerous material down the hole tell the people that the radiation and chemicals will not harm them, and will not seep up into their ground for thousands of years. And in the short run, people benefited from the hole, making profits from those who spent money to dump things into it. However, in the end, what went into the hole eventually is dumped out the other side, which turns out to be right on top of the people who first discovered the hole. 

Why is the title of the story "He-y, Come on Ou-t"?

In “He-y, Come on Ou-t,” a mysterious hole opens in the ground of a village after a storm. Curious onlookers try to discern more about the hole—its size, depth, function, and so on. Thinking that it is a foxhole, a young man shouts down into it, “He—y, come on ou—t!”

His exclamation—and the title of the story—is significant because it sets off a chain of events demonstrating man’s cavalier attitude toward Earth. By the end of the story, writer Hoshi reveals that man’s greedy, irresponsible, selfish nature will be punished. The later echo of this titular sentence foreshadows the people’s deserved fate. Garbage that they carelessly discarded will return to them; poisonous waste and human refuse will literally “come out” of the sky and rain on them.

Initially, everyone wonders how deep the hole is and if it has a bottom. When he does not hear an echo after calling into the hole, the man tosses in a pebble. Then the falling pebble makes no sound, leading onlookers to conclude that the hole is unfathomably deep and bottomless.

This titular exclamation unleashes a curse on the villagers. At first, though, the people believe that they are lucky. The hole becomes a lucrative attraction for the village because it makes the perfect disposal site for nuclear waste.

The people of the village were a bit worried about this, but they consented when it was explained that there would be absolutely no above-ground contamination for several thousand years and that they would share in the profits. Into the bargain, very shortly a magnificent road was built from the city to the village.

Very quickly, though, the hole is transformed into a site for disposing anything unwanted—classified documents, corpses of test animals for contagious disease experiments, emotional debris, incriminating evidence, and more. The people grow into wasteful profligates:

They concentrated solely on producing one thing after another. ... Whatever one wished to discard, the hole accepted it all. The hole cleansed the city of its filth; the sea and sky seemed to have become a bit clearer than before.

They dump anything unwanted into the hole, all in the name of money and convenience. By the end, however, their utopia is in jeopardy. Despite seeming to clean up their environment and ridding themselves of dirt, they will be punished.

One day amidst the shiny new construction of skyscrapers, a worker suddenly hears from above,

“He—y, come on ou—t!”

Unable to hear the source of this call in the blue sky, he turns back to work. However,

from the direction where the voice had come, a small pebble skimmed by him and fell on past.

The man, however, was gazing in idle reverie at the city’s skyline growing ever more beautiful, and he failed to notice.

This ominous ending portends the return of all the detritus. The oblivious people are too wrapped up in signs of their material gains and will be buried in an avalanche of their own waste.

Explain the irony of the ending in "He-y, Come On Ou-t!"

The irony at the end of “He-y, Come on Ou-t!” occurs as the villagers are finally faced with the consequences of their careless actions. The hole at the center of the story seems bottomless. At the beginning, a young man yells down the hole, which appeared after a typhoon, and throws in a pebble. No one hears an echo or the sound of the pebble hitting bottom. The villagers and their neighbors soon come to believe that they have the perfect solution that will allow them to get rid of everything they don't want. They can simply throw it down the hole, and it will disappear forever.

They begin doing just that. Everything from toxic waste to classified documents to letters and diaries goes into that hole, and everyone thinks they have gotten rid of their unwanted items for good.

But at the end of the story, a voice rings out from the sky one day with the very shout that the young man yelled into the hole. A pebble soon follows. We readers realize, as the villagers soon will, too, that everything that has been dumped into that hole will soon come out of the sky right onto their heads and very much back into their lives. They have gotten rid of nothing. It will all come back to haunt them.

Here is the delicious irony of the story. What seems gone for good comes back around. Appearance and reality are two different things. Throwing something away rather than dealing with it properly is no solution at all, as the villagers will soon know.