So, some important information: this is most likely based on cryptic stories that circulate on the web in Japan. They're just short little stories where there's a little detail that's just a bit off.
Given this manga is only 4 panels, the answers can be way more in our face than when it's a full text post.
If you're just looking for a plain old horror manga, just stop reading this one instead of complaining. Horror isn't the main point, these types of stories are like riddles.
I agree with this (sorry for shaving your post down a bit). This is a bunch of ideas that aren't very developed because of the ultra short format. I guess the mangaka had to deliver a lot of them in a short time to get paid enough to survive, so it's a given that some of them are throwaways. There are some with potential though, even if it's hard to notice in this form.
Chapter 6 is basically the plot of one of the most lauded crime novels ever written: "The Hollow Man" by John Dickson Carr. I describe it in the ch.6 forum.
I'm honestly surprised by the people who complain and still keep reading, admittedly it doesn't take much time but still?
Especially those who complain that there are Japanese puns that are hard to translate to English in a manga written in Japanese, for Japanese readers? I was going to write a bit about that but now I can't really be bothered.
This manga is not great, but not that bad if you take it for what it is. And don't bother reading the explanations, they're mostly superfluous. I skipped them except for a few Japanese puns I didn't get.