Yeah, I'd agree on Shinta's analysis. Misaki is clearly crazy, but there was a consistency to her craziness: only killing villains. So, once she made herself one, according to her methodology, she needed to make herself her next victim. But there was also one last factor: She had experienced killing the villains, she had experienced killing the innocent, the only thing she had no experience of was killing herself.

It kind of annoys me necro-Polka is goody two-shoes. It might be better than being a super villain, as I don't really enjoy watching really evil main characters, but he could have been a bit more selfish. Now it feels like he's willingly playing Kuraki Risa's game, even though Risa was the only who accepted the deal for Polka's murder. It's not like she could really threaten him anymore, either. It was pretty pointless to leave all of those criminals alive as well, and in such a strange state. At the end of the day, he's hundreds of years old, so he should have limited patience for things that don't interest him. I'm not sure what kind of peaceful life he's expecting by relying on a gang of violent assassins.