this series might be taking one too many liberties
just in this chapter Flay showed he doesn't know the face of the hero, who not only is a key figure of his past, he is also the most famous person among humans, so much so even the demon king's daughter knows how he looks, and he mistakes said person with the demon lord
and the demon lord didn't even bother name himself just so we get to see this conflict... "why the hell do i have to be stopped just to see my own daughter?" how about you say that out loud for starters?!?