The Iron Titan - Mission to Shiganshina (1): Attack on Titan FanFic

There are cities outside of the three Walls that haven't even seen a Titan before! The Recon Corps embarks on a mission to figure out how the towns, Evergreen and Brook, have avoided the Titans for so long. They arrive a little too late; both towns are under attack by the Titans. What's more, the Military Police still want Eren and there is a new threat to the Walls.