Grim Hunt is a story written by Sora Junko. It ran in Issue 14 at http://s2b2.livejournal.com/74574.html, and is mirrored at http://www.shousetsubangbang.com/mirror/grim-hunt/.
This is the fourth (holy cow!) story in the Grim series. You may want to read the previous chapters before reading this one, but this story does stand on its own.