On an alternate version of Earth, humanity has retreated behind three tiers of 160-foot-high walls to protect themselves from giant humanoid monsters called Titans. These creatures don't seem to be sentient, and appear to exist only to free manga and eat humans. For over a century, humans lived this way, protected by the walls - until a 200-foot-tall Titan appeared and broke a hole in them. The series follows protagonists Mikasa and Eren, as well as the other new recruits of the Survey Corps, as they work to stop the newly adapted Titan invasion.
Attack on Titan started in 2013, but it took a four-year hiatus before returning with a 12-episode second season in 2017. Due to its combination of bloody horror, action, character drama, and politics, the show has been responsible for getting a lot of people hooked on anime.