That sort of thing doesn't occur to Sizhui, regarding the difference between what death and exorcism would mean for Koro; exorcising would be driving him out of the world, sending him back to where he came from, but death... well, he would imagine it's something else for a demon like him, one he hasn't ever encountered before today.

Unfortunately for Koro, he just so happened to step into a cultivator's trap, but lucky for him as well, it's someone like Lan Sizhui who will listen rather than instantly taking action against him. Any of the other disciples would have acted and asked questions later.

If he's only here to live amongst the humans without harming them, then what's the issue? He could be given that chance, but the second he tries anything underhanded, that's when a wrath worse than the Hell he speaks of would come down upon him. Yes, demons could live peacefully alongside other beings, it's simply the fact of whether they will or if it's all a ruse.

The defeated tone does have Lan Sizhui relaxing further, his brow furrowed, the hand he's holding his sword with slowly lowering to his side. It sounds harmless at first, maybe even like he wants to be somewhere better than where he came from, except the moment he mentions feasting on his flesh, Sizhui's up in arms again, eyes wide and his unoccupied hand lowering to rest at the qiankun pouch at his side.

“You— you want to eat me? That doesn't sound harmless at all!” Sounds like the direct opposite of it, to be honest.