The MiA author is definitely a sex pervert (the volume extras leave no question of this), but children being put through incredibly fucked up dangerous body horror situations because most adults in the setting are useless and/or evil is like half the point of the story. It really does need that.
The fanservice stuff, on the other hand, is either just Japan being Japan, or further playing into the lost innocence theme above. I think one can convincingly argue for it being a little bit of both or entirely just the former, but it almost certainly is not entirely just the latter.
The MiA author is definitely a sex pervert (the volume extras leave no question of this), but children being put through incredibly fucked up dangerous body horror situations because most adults in the setting are useless and/or evil is like half the point of the story. It really does need that.
The fanservice stuff, on the other hand, is either just Japan being Japan, or further playing into the lost innocence theme above. I think one can convincingly argue for it being a little bit of both or entirely just the former, but it almost certainly is not entirely just the latter.