I think that's a problem with the world itself in this case. It seems that people with the title of heroes aren't actually Heroes in how we know them, but people simply born with a specific type of power, ala Phoenix.
I think that the title "hero" has different meanings in all kinds of these type of mangas. Sometimes it means saving people or only defeating the demon lord. Other times there is just a very strong type of magic needed to become a hero, like with a saint or saintess.
In the case of this manga the hero's job is just to defeat the demon lord. ┑(￣Д ￣)┍
That new girl? Yeah, I see light in her (or 'dark' in her bc black magicians seem to be the good guys now...) She's smart enough to figure out what those shitheads couldn't seem to get while it was looking at them in their eyes.
U wanna know who I'm really not into rn? The hero - seems so fake. Like he wants the title of a hero, but doesn't understand what being hero really means (i.e. saving ppl, helping others, chivalry and so on.)