I dont think its to kill Soowon? I dont believe Yona would be a good King and I dont want the dragons nor her tied to that responsability. However, it is getting annoying. Why save the woman?! It is a big problem she knows Soowons secret and her hatred to Yona! If she can't ignore it! Dont get involved in the first place!
This is getting so boring. There's a bunch of lame chapters, then a couple of amazing chapters, then the cycle repeats. Sadly, in the boring chapters, there's a bunch of important information so it's unskippable.
I'm more or less convinced that Soo-won hasn't read Yon-hi's memoir or Il' letter. He's too surprised when Yona talks of things she isn't supposed to know. Also, he doesn't seem to be aware that Il knew Soo-won was going to kill him from the very beginning (and that all this time he had been playing to the tune of the prophecy like the tragic Greek figure he is).