I think this could be beneficial. If N kills him then it'll be bad for the kanzaki as people would think worse of her. N wouldn't want that. In fact he'll hate it. Of course N is already shown to be unstable so who knows?
@mommunism Everything in manga has been done before there is never going to be a original trope anytime soon. It's all how it delivers the tropes it has and I'll say this one is doing good right now.