Attack on Titan: Lost Girls(進撃の巨人 LOST GIRLS)

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