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 one chapter and a prologue published.

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

Plot
Seventy years before the fall of Wall Maria, a Titan appeared inside. People were instructed to keep this incident a secret, however.