The original manga by Chūya Koyama began serialization in Kodansha's Weekly Morning magazine in December 2007 and has released 28 volumes as of April 2016. The manga is available in digital form in North America and Europe from ComiXology and Amazon as both volume and SimulPub chapter format. It is also currently available in English as part of a read-only subscription from Crunchyroll and Kodansha.[6] Again, as a SimulPub