Weekly Shōnen Magazine
A side story series, titled "", began in the 2009 28th issue of Kodansha's "Weekly Shōnen Magazine", published on June 10, 2009. The manga finished in the 2011 42nd issue of "Weekly Shōnen Magazine", published on September 14, 2011. Kodansha compiled its chapters into nine "tankōbon" volumes, released from October 16, 2009 to November 17, 2011. A three-chapter spin-off, titled "Black Diamond", was later published in "Weekly Shōnen Magazine" in November 2011.