Ah, my mistake. When I saw this pic under when_you_see_it, all I knew about the series was that Mami got beheaded somehow; in particular, I didn't realize that white tuft of whatever-it-is was actually part of her hat. Conclusion: some white-haired person, presumably the killer, is holding up Mami's head in front of her own. (Which would still be a really awesome and creepy idea for one of these "yandere trance" pics, if you ask me.)