a manga based on this was published by ascii media works between 2007 and 2013. bandai entertainment licensed the manga and released it in english in north america. a series of four light novels was published by shogakukan between 2007 and 2008. a nintendo ds video game was released in october 2007. two animated film versions were produced. the first premiered in japanese theaters on september 6, 2008, and the second premiered on april 25, 2009.