The Monotsuki isn't the only one wanting a taste of Hime
I'm gonna say the obvious and predictable, guy(?) in the tube is either part of a secret conspiracy that controls the world behinds the scenes, or he's actually the person who caused the apocalypse long ago and is trying to properly come back to life.
I suspect it's the latter and that Isana sister, who I forget the name, is destroying cities to try kill him, she and whoever she's working with is being so extreme because they have no choice, since if he gets better he will destroy the world again.
Not gonna lie, I hope the villain is a woman, it's almost always a man lol
Also, surprised the tribe girls have face, honestly suspected their face would be inhuman in some way.