It maybe true.... but previously So won said he has had no interest in the dragons rather supress them if necessary.... I think they will try to kill the dragon by ambushing them....
Not likely since now Kouka people know by word of mouth of the soldiers that the dragons fought to save them. It would cause dissenters and So Won is clever enough to avoid that situation.
On the other hand if he let the dragons live he could say "Yona, I keep them alive, I let you free so that all of you can go and save the kingdom, but let's become allies and sto antagonizing each other"
So both Yona and the dragons would be neutralized from his point of view and they would be free and happy
But not Yona ..... she has to live with her fmfather's murder and it is clear that nobody wants her in the palace... and I think advisor has his own motive too
I must say that the advisor's move was quite wise. From a strategical point of view it's perfect and I honestly think that if Yona had a bit of political knowledge she would agree with it.
Don't get me wrong, as a reader I'd rather see Yona and Hak together, but if I were a Kouka citizen I'd be happier like this. It works better for the kingdom.
Naturally It would work only if both rulers had the same power, otherwise Yona's power would be suppressed and Kouka would lose an important piece for its growth. That means that something must be done to make the advisor lose his power. In fact I think that So-Won would agree to make Yona indipendent. Two wise rulers ar better than one.
Two wise rulers on the same side are better than to wise rulers who oppose each other