Shingeki no Kyojin (進撃の巨人) or Attack on Titan. Several hundred years ago, humans have been eliminated almost completely extinct by the Titan. Titans are generally high as four or five-story building. They seem to have no intelligence, like to eat human, and the worst is that they look happy always while hunting. Survivors from being eaten live by detention itself in the city that was protected by three concentric walls higher than the largest titan in that period. As time passed, the city where people live happily free from Titan over 100 years in the present era.
One day, a boy named Eren Jaeger (エレン・イェーガー) and adopted sister Mikasa Ackerman (ミカサ・アッカーマン) have witnessed something of a fearsome when the first wall were destroyed by a massive titan that higher than the wall. While the other titans invade, Eren and Mikasa saw his mother was eating inevitable. The terrible incident caused him to vow that he would kill all titans.