 Futabasha published 13 "tankōbon" volumes between December 12, 2005 and June 12, 2013.While the aforementioned pilot is not considered part of the ongoing series' canon in spite of the shared name, largely identical main cast, and common central theme, many situations and ideas initially introduced there were revisited in the eventual manga series—and thus incorporated into official continuity—albeit in (slightly) altered or expanded form.Digital Manga has licensed the series for publication in North America, and originally planned to publish it in omnibus format under its Project-H imprint.