Based on last page's message, looks like the manga is doing really good lately!
Next issue we'll finally know what happened to the world. Any theories now?
So I got a big theory, maybe a little crazy, but roll with me. What is the earliest theme of the series?
Things are not what they appear to be. What was an orphanage is actually a plantation. This element has appeared time and time again, even with these new characters, who had plenty of sinister painting shots to make you doubtful(and maybe still doubtful) of their true intentions. So with this in mind, my big theory is this.
I don't think we're on Earth. There is no reason to think that outside of the fact there are trees. And even then, the trees don't quite look
right. There are animals more akin to demons all over the place, hostile agriculture that shares design elements closer to the demons, and even Minerva's books are of him going on adventures in
foreign lands. And when you think about it, what makes more sense? Demon's invaded, took over, and cultivated Earth? Or Demon's started "growing" these humans they found on their own planet on Plantations? My personal theory that I've held onto for awhile, and we'll see how true it is next chapter.