World's End Harem confusing situation and how to read it?

[Martinho]

First post in the forum, sorry for any mistake
A friend of mine recommended World's End Harem, I read it a little bit, it seems interesting, but when I saw the related works I became confused.
There's a spin-off, World's End Harem Fantasia, in a fantasy setting with completely new characters and story, which made me confused, but whatever it was a spin-off. HOWEVER, there where other 2 spin-offs of this spin-off
There was World's End Harem Fantasia Academy, a spin-off with the characters from the first spin-off in a High School setting, and there was World's End Harem ~Britannia Lumière~, a spin-off of World's End Harem Fantasia, with new characters and stories in a different fantasy setting.
So I was wondering, after my head fucking melted, is there a way to read this in order? How can I read it? To anyone who knows, please tell me.

 

[Andraker]

They don't seem to be that much related, you can read it just as a different manga from the same author.