[He takes a long, measured breath, then gestures for her to lean back on the cot while he fetches a cloth.]

Kaori...this is going to hurt a lot. You'll need this cloth to bite down on, and I'm going to have to ask Vash to hold you steady so you don't thrash and make things worse. [He's not sure how she'll react to being told she needs to be restrained, but he's running out of options.]

I...really don't want to hurt you, so I'll ask one more time, okay? If you let me medicate you, you won't feel anything else but a prick. You'll fall asleep, then when you wake up, me and Vash will be here, and you won't hurt at all anymore. You can trust me.

[He pauses, hoping that she'll use the moment to reconsider. Then he offers a weak smile.] But it's up to you. I promised, right?