Hajime Isayama has announced via Twitter that he is canceling the previously announced Attack on Titan prequel.
The prequel, titled Attack on Titan FLY, would have taken place 100 years before the story of the main series. He cited that it would take a lot of determination to draw it and with the way the main story went, it would not be a good fit, therefore, he didn’t make any progress in writing it.
Right now, Isayama is focused on creating a one-shot, stating that it should be his goal to make fans happy with it.
Source: CBR