Boogiepop (ブギーポップシリーズ Bugīpoppu shirīzu) is a light novel written by Kouhei Kadono and illustrated by Kouji Ogata. It has multiple forms of media with interlaced stories, from the original light novels to anime and manga. If you'd like to contribute to the wiki, please refer to the above links.
There is an urban legend that tells of a shinigami that can release people from the pain they are suffering. This "Angel of Death" has a name—Boogiepop. And the legends are true. Boogiepop is real. When a rash of disappearances involving female students breaks out at Shinyo Academy, the police and faculty assume they just have a bunch of runaways on their hands. Yet some students know better. Something mysterious and foul is afoot. Is it Boogiepop or something even more sinister...?
Five years ago, a string of grisly murders shook the city to its core and now the rumors have begun once more. Boogiepop... Everyone knows about Boogiepop: meet her one dark night and you are taken. People tell each other the stories and laugh: no one believes that she can possibly exist in this day and age. Still, strange things appear to be going on and the darkness is taking on many forms. Something is out there. Are you safe?