THE EMPRESS OF VANHEIM

The more powerful the Chancellor become, the more uneasy Edward became. He knows that he needed the Chancellor help to withstand James influence

That is one of the reason why he had been pretending to be timid all of these years. He did not want the Chancellor to see that he could fight

But this time, Edward believes that Aero had known certain things that he hid. 

If he did not, why would Aero not come back earlier and even hide himself from him? 

If he had returned, even though Karak would insist the Empire to give the Chancellor back to them, with the power of the Empire, how could Karak insist for too long?

It is not like the Chancellor couldn't clear his name by returning to the Empire.