Back in August, it was revealed that Hiroshi Seko’s Attack on Titan: Lost Girls spin-off novel would receive an anime adaptation; three OAD episodes. The YouTube channel of Weekly Shonen Magazine has uploaded a trailer to the first episode, Wall Sina, Goodbye.
Each 25-minute episode will be packaged alongside the release of the Attack on Titan manga in Japan, the first of which will be released with volume 24 on 8 December 2017. The second episode will be released with volume 25 on 9 April 2018. The third episode will be released with volume 26 on 9 August 2018.
The novel focused on the characters Annie Leonhart and Mikasa Ackerman. Wall Sina, Goodbye is listed as episode 16.5A and has Annie taking on a job to find a missing person.