Exactly. They’re part of a series called ５分後に意外な結末（ごふんごにいがいなけつまつ) or “a surprise ending in five minutes”. Basically, a collection of short stories around ten pages long, where each story has a surprise ending of some sort. They’re not always really great stories, but they expose the reader to a bunch of different settings and story types. I like them because they’re just about at my level. Although I should probably call them “a surprise ending in a half hour” given that I still need to use a dictionary for a full understanding.
Be careful though, because one of your links was for the ５秒後に意外な結末 series, which would be something like “a surprise ending in 5 seconds”. These stories are only a couple of pages long, and just don’t seem as interesting or useful for learning Japanese to me.
The Intermediate book club read one of the “five minutes” series books here.
Ah, yes, thanks. I keep making that error.
Also thought I’d mention that it was a video post of yours here that first lead me to the 意外な結末 series a few years ago. 