When a Colossal Titan breaches humanity's first line of defense, Wall Maria, all seems lost for the surviving humankind, until a new Titan appears and surprisingly begins to slaughter its fellow Titans. Original.
Hajime Isayama first published Attack on Titan in Bessatsu Shōnen Magazine in 2009. It became a sleeper hit and won the Kodansha Manga Award in shōnen category in 2011. This is his first manga.