Attack on Titan: Before the Fall (Manga)

Attack on Titan: Before the Fall (進撃の巨人 Before the fall) is a currently ongoing manga by Satoshi Shiki, based on the light novels by Ryou Suzukaze. This manga serves as an official prequel to main story by Hajime Isayama. There are currently three chapters and a prologue published.

Kodansha USA has licenced this manga and will start distributing it, starting on March, 2014.

Plot
This story takes place 70 years before the manga story starts. Seventy years ago a titan appeared inside the wall. People were instructed to keep this incident a secret, however.