Well now it realy seems...
The puzzle of AkaYona plot is being solved.
Like it almost says that lady Kashi pretty much could be killed for being to vocal about her child as Hiryuu incarnation.
It could be a source of conflict between the royal brothers. It might be why Yu-Hon chased priests out, as they more likely agreed with the queen, than not.
And also it explains why Il, holding public prayers and stuff didn't return the priests back — not to endanger Yona.
But it does not explains what Su-Won is keeping to himself. Since he personally has been told by his uncle, that Yona is Hiryuu. 1)Why to him? If Il tought the boy aimed for the throne, it was dangerous thing to say. 2)If Su-Won knew that, he probably knew details of Kashi's death and if Yu-Hon was involved, knew as well, that Il had a point killing his brother. So it could make all the revenge thing pointless. And it means Su-Won had reasons to act here and now complitely regardless. But what? Marriage of Yona? To whom in the world then, if it shook coup party so bad? Il didn't mention if he already choose someone.
I would almost believe Il knew about the coup and it was his strange way to make Su-Won his successer instead of Yona in hopes that Yona will be seen as weakling with no actual power and Su-Won would sent her away in some safe place (like, she is a god, she'll survive not being near the throne). If not the door, that left open and the princess left unsupervised. It changes everything. Coup was a surprise attack for Il. So he probably planned just to keep Yona as a trophy queen gods would help anyway. But in this case why not with Su-Won as a king?..
And what the Xing arc meant to the main secrets?