"Attack on Titan" season 2 is assumed to feature two story arcs, one reason behind the delay of its release to 2017.

According to Movie Pilot, "Attack on Titan" season 2 is set to include two story arcs, which are entitled "Clash of the Titans" and "Uprising Arcs." As per the report, the former story arc will see Eren and the group face a mysterious team of Titans who appear inside the wall.

As per Ecumenical News, four arcs are needed for a season to pursue; thus, having two arcs is a potential reason behind the delay of "Attack on Titan" season 2 release. However, the series creators and producers have yet to announce the official details with regard the story line.

Additional theories on "Attack on Titan" season 2 have also surfaced and one of them is the Titans' backstory, according to Christian Times. It can be recalled that the first season introduced the Titans as naked giants who go to villages and eat humans for unspecified reasons. As per the publication, the second season will present an explanation to their origin and behavior.

In other news, earlier reports revealed that "Attack on Titan" season 2 is set to be released in the latter part of 2016; however, new details have surfaced, suggesting that the release of the forthcoming installment has been moved to Jan. 2017.

It is revealed that "Attack on Titan" director Tetsuro Araki is working on other projects, aside from "Attack on Titan" season 2, which leads to another reason behind the delay. According to Game N Guide, Araki is currently working on "Kabaneri of the Iron Fortress" and this prevents him from completing "Attack on Titan" season 2.

Overall, "Attack on Titan" season 2 is set to air in Jan. 2017.