the kids were not innocent at all; they know what they were doing and what was going to happen to the visitors/victims. that whole village is messed up morally.
What manga do you think you're reading lol? What's probably going to happen is that the hero is going to cast an illusion to make the parents look like strangers. And those little monsters are going to laugh in their parents face as they die from thirst, just like their parents raised them to do.
Either that or they're gonna kill and slaughter them, only to realize they killed their own parents when the illusion wears off.
Shame the chapters are so short. Really feels like this manga would benefit from each "arc" being a long chapter of several dozen pages rather than what it is right now.