It's a fair question and Himeka is not opposed to discussion before battle. It would be easier for the both of them if he simply gave a casket over, after all, but she does not believe anyone tasked with their safety would be so easily persuaded.

She keeps her battle ready stance, but makes no indication she is about to attack. Not yet.

"They're upsetting the natural balance of the Singularity." At least that was the implication the Council had made.

Though she has never been to the Free Cities, she would assume that their lack of reliance on magicks would be unappealing for someone who has the still-lingering remnants of recently cast magicks on them. (And it would certainly be a boon for someone from the Free Cities to have absconded with not one by two caskets already, wouldn't it?) So she ventures a guess--

"You're working with Thorne, aren't you?"