Attack on Titan

The last of humanity lives inside concentric walls, hiding from Titans: enormous humanoid things that eat people for no clear reason. For a hundred years the walls held. The first season opens on the day a colossal Titan kicks a hole in the outermost one and the giants pour in. Eren watches his mother die and joins the army to kill every Titan there is. What starts as a simple survival-horror premise keeps pulling back to reveal a larger, uglier shape, and the show is built so that each answer makes the world feel less safe rather than more.