...The author/story is inconsistent. Allen himself clearly stated that the children had the Hero and Demon Lord sigils when he picked them up. But for the rest of the story, despite making a clear effort to hide the marks as evidenced by bandaging their hands, he's conveniently clueless to their real identity?
It'd be one thing if he never knew what the mark was initially and there were no records so he also couldn't find it out later. But as it stands, unless we're to just ignore the first chapter happened, this dude's a big dumb dumb.
I liked the story's concept, execution is meh.