Go Nagai has done some kid-friendly stuff before, but he's also a big-time perv.
gee, i just finished reading this and a little kid get decapitated

this isn't the first time i read an old ass manga where a kid dies an horrible death, old ass manga are serious stuff
the ending is a downer too "yup! humanity is fucked, THE END!"
you know i feel like i've done a disservice to this manga by calling it "a punchy thing manga" because there is like 2 fight in the whole manga, it's more of a mix of an horror manga and an incredibly bleak pessimistic dystopian manga, in the end it's humanity itself that goes crazy at the horror of the demon wars rather than the actual demon murdering everybody, i tought that was a nice way to turn it into something different from the usual manga's