The limited edition of volume 14 of manga Shingeki no Kyojin
, to be released on August 8, 2014, will contain another OVA
. The content will be an original story based on another story of the "104th Gunren Heidan-hen," which tells a backstory of how the 104th Trainee Squad got together. Volume 13, which includes an OVA that begins with the story of the "104th Gunren Heidan-hen," will be released on April 9, 2014.
Source: Presepe Page