BTW, there is already a manga adaptation for this series, in the Comic Ride magazine. Chapter 0 (the prologue, which mixes part of WN ch.01 with content from later chapters) is available for free reading.
http://comicride.jp/gluttony/ (scroll down and click on the big teal
第0話)
^--- BTW, this is the official magazine link, so there shouldn't be anything wrong with posting this link.