I vaguely remember reading a story as follows (memory is hazy, so I might be wrong on some things or conflating two separate stories):
A man goes to another man's house, where there is a hole in the basement. They spend some time examining the hole, which is pitch-black. One of the men even goes inside, and the other side of the hole seems infinite. This hole starts multiplying, with holes eventually appearing on humans and bringing about the end of humanity. I believe it was a Japanese short story, but I only found “He-y, Come on Ou-t!” by Shinichi Hoshi, which is definitely not it.
Again, I might be conflating two separate stories here, but any help would be appreciated. Thank you.