After reading the manga description, I was wondering how can there be so many chapters just to kill five people. But apparently the Unit 731 grandpa turned the MC into a monster, who can't simply kill the targets and be done with it, like a pro, he needs to formulate complicated plots to torture them to death. No wonder the story decided to include the cops as well. Well, fine, if that's what the author, publisher, and audience all want, but it's really unfortunate the author can't pull this off without the plot device character, Chizuru Azuma.