Attack on Titan (進撃の巨人 Shingeki no Kyojin) the 2013 anime was adapted from the eponymous manga, created by Hajime Isayama. The series began in Kodansha’s Bessatsu Shonen Magazine on September 9, 2009 and has been collected into 17 tankoban volumes as of August 2015. The anime was produced by Wit Studio, directed by Tetsuo Araki. (Wikipedia)
As the story goes, the surviving remnants of humanity lives in cities enclosed by massive walls. The walls are there to fend off the titans, colossal humanoids that eat people. Eren Yeager, his adoptive sister Mikasa Ackerman and their friend Armin Arlett live in the outskirts of the walled city.
One day, a colossal titan breaches the wall and the giants come streaming into the city. The town is laid to waste. The young trio’s lives are forever changed. Bent on revenge, Eren and Mikasa vow to join the Survey Corps, an elite group of soldiers who fight titans outside the walls. (Shingeki no Kyojin – Wikia)
Attack on Titan streams on Crunchyroll, Hulu, Netflix and Funimation.