[ ... there's a long pause as he assesses all of that. he doesn't say anything for a while. ]

... Can't see how you'd have anything to gain by lying to me about all that.

[ it's pensive. he's not stating outright that he believes shirasu, but he doesn't seem to doubt him, either. ]

So why not just try and kill her outright? Either way, you were hoping for the partner thing to save you. Is she that much stronger than you?