Slime just sitting on his head, casually eating his hair all day. She'll be the most powerful being in the end.
@AfresherPerspective
This is a flimsy excuse for hentai-type of isekai. Don't take the characters or world too seriously. Or seriously at all, it's a huge fucking joke.
That said, I'm sure the reasoning would be that the human is considered a threat to all established authority and power, and has a small army of monsters. Monster army led by world-shaking titan of mythological godly power whose body is worth more than continents = Quick, kill 'em now, he's right in our backyard, can't have something that strong in our area that we don't control otherwise we can't be said to actually control our own territory or protect our people. Plus, if we suck on his toes we'll get superpowers.