Perhaps Nezumi doing it herself might be more effective to get over the trauma and wash away his influence over her.
I'm also worried about the kidnapped children. Handing them over to the yakuza group is a no no, they might be against human trafficking but had no qualms in using Nezumi and Midori as child soldiers. Handing them to the police without involving themselves and without the support of the yakuza will be very tough (I also bet some of them might have been sold off by their family, so going back to that would be bad). And we know Nezumi in her current "programmed killing machine" state is very capable of killing them if it simplifies their situation...