I can't help but to think the general is plotting to overthrow the royal family. He has been noted by everyone as being highly ambitious which make his appointment as marshal concerning as he would have near absolute control of the military. Combine that with his wife's political savvy and cunning he may see the opportunity for a coup. I know Aura wants to make her job easier for both her families sake and as royalty, but he seems too big a risk.
Additionally, his strategy with the legion dragons failed to account for the possibility that they would be driven into population centers that were not on guard which caused more civilian casualties. Honestly they should have a more veteran military strategist as marshal and leave the general who revels in fighting as a field commander. The way things are going, I can foresee a potential internal conflict where Freya's bodyguard and the general fight to the death in his attempted coup as their power was compared near the end of the legion dragon arc.
I really hope the northern kingdoms come at the twin kingdoms from the eastern portion of the continent and thwart the twin kingdom's schemes of trying to manipulate Zenjirou and involving Carlos. If they were at least honest with their concerns about the northern nations as a potential threat to the continent I would be more accepting of them. As it stands, they are trying to use Capua as both production and fodder in a potential war with the north. For now the crystal/marble production should be halted and methods sealed.