Previous reports have already indicated that "Attack on Titan" season 2 main story line may not be released until the rumored August 2015 date. To fill the void, Wit Studio has confirmed that it will instead be releasing a prequel spin-off to be called "Attack on Titan: No Regrets, Birth of Levi" which is also reported to arrive this December 2014.
As suggested in the title, "Attack on Titan: No Regrets, Birth of Levi" will delve into the history of Levi's Survey Corps prior to Eren's and Mikasa's involvement in the force. This will serve as a prequel to the main story by Hajime Isayama.
Isayama's "Shingeki No Kyojin," which is Japanese for "Attack on Titan," is a story set on a post-apocalyptic Earth where humans are threatened to the brink of extinction by man-eating giants called Titans. The plot revolves around a certain Eren Yeager, a member of the Scouting Legion, whose motivation to fully-annihilate the giant race was driven by the thirst for vengeance. When he was young, Eren witnessed the demise of his mother at the hands of a "Smiling Titan," a variety of Titan that measures 14-15 meters.
The anime show is based on the manga written by Hajime Isayama whose encounter with a drunken man has inspired him to write "Attack on Titan," according to AnimeNewsNetwork.com.
The TV show adaptation first aired April 7, 2013 and ended in September 28, 2013. It has then gained a throng of followers eagerly waiting for its second season.
Official statements on the release of "AoT" season 2 is yet to be announced but rumors are pointing out for a July or August 2015 release date.