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.
Original title Attack on Titan: Lost Girls
First air date Dec. 16, 2017
Last air date Aug. 09, 2018