Attack on Titan: Ilse's Journal
Bundled with the 12th and 13th limited-edition manga volumes.
Episode 1: An old journal is found by Levi and Erwin when they conduct the surveillance operation outside the wall. The contents of "Ilse's Journal" result in some unexpected actions from Hange.
Episode 2: Another story of the 104th Trainee Squad.
Episode 3: Will depict a "memorable episode before the 104th Training Corps became unified."
(Summaries provided by MyAnimeList.net)