Storyline
Release Date
- Season 1: October 7, 2007 – December 30, 2007
- Season 2: January 6, 2008 – March 30, 2008
- Season 3: January 4, 2009 – March 29, 2009
- OVA 1: June 23, 2009
- OVA 2: October 5, 2012
- Season 4: January 6, 2013 – March 30, 2013
- OVA 3: August 6, 2013