OVA: Lost Girls: Wall Sina, Goodbye - Part 2

Shingeki no Kyojin OVA that is bundled with manga volumes 24, 25, and 26. Several hundred years ago, mankind was nearly extinct because of the Titans. The Titans are big, have no intellect, hate people, and worst of all, they think of humans as food. The survivors of the humans built a very high wall to protect them from the Titans.