The Britannia Empire has attacked nautral Japan. It has confirmed its role as the world's only superpower. Japan has lost its freedom, its flag and even its name - Area 11 is now unseparated part of the empire and it has to obide the highest ruler of empire.
The Britannia empire is ruled by the one huge royal family with precisely given the successing rules. Thats why some younger heritors dont hesitate to take an action in order to get rid of the people above them, just to get more power.
In Area 11 a lot of political mistakes were made and with the behavior against the Japanese, the empire made a lot of enemies, who are willing to give their lives to protect their families and way of life. The rebels are now allying with the mysterious Zero, who brings them to the first great victory against what seemed to be an unbeatable enemy.