There are many options for an alternate ending to "He-y, Come on Ou-t" by Shinichi Hoshi. The original ending could be changed entirely, or you could just pick up after the story ends.
For example, you could change the story so that the hole fills up, something comes out of the hole, or the characters suffer some other kind of consequence for dumping all of their undesired items into the hole. Alternatively, you could have the construction worker respond when he hears the voice shout down from the sky. You could also write an ending where people start to realize they shouldn't drop things down the hole.
Overall, there are infinite possibilities here—I hope you find the ending option that most inspires you!