"So listen, there's a guy who fell out of the sky, didn't speak our language, killed a dragon in one shot with his bare hands after having flame breath poured on him and shrugging off high class petrification magic, and then ripped knowledge directly out of that dragon's corpse so he could speak and understand us. He claims to be a reincarnation of a demon lord from the distant past, and this holy relic owned by the guild that detects all lies says he's telling the truth. He is literally more powerful than a company of 100 of the most powerful people in our kingdom combined, while naked, unarmed, and wearing rags. There's also a prophecy saying that a demonic king of calamity will arrive on the exact date he showed up, under those exact circumstances.
"So obviously, we think he's lying, and something must have just deeply traumatized this unfathomably powerful person who turned a dragon inside-out and shoved his hand up it's ass like it was a muppet. He must merely think he's the demon king reincarnated, because, you know. That would be crazy. Almost as crazy as punching a dragon so hard all of it's internal organs explode and then eating it's soul to gain all the knowledge it possessed in life. So naturally, we're assigning a level 1 titty elf with the Job Class of Clumsy Fuckup to keep an eye on this person that we flat-out admit could solo our entire kingdom. Also, she's a magnet for all the bullies and assholes our society and system cannot or will not deal with, so obviously we should leave her in the company of the literal demigod who does whatever he feels like at any given moment. This is a great idea, and nothing could possibly go wrong."
Gonna be honest. I'd be rooting for the demon king even if he wasn't the protagonist, because I feel like he needs to conquer the world to save these people from their own suicidal amounts of stupidity.
Also, the fat titty mommy fox being a genuinely reprehensible and unlikable person is interesting. The characters are entertaining, if nothing else.