Soowon is a very complex and interesting character, and one of his traits I like a lot is his idealisation of Yuhon because it actually created a really big issue of Soowon.
Of course, Yuhon was his role model when he was a child, but what about 18 y.o. SW? Did he think of his father so much, to the point that he started questioning some of his words or actions? Or does he still see his father in a perfect light? I've got these questions because while SW is a shrewd and level-headed person, he's been shown to be biased for the first time (as far as I remember; it's been a while since I've read AkaYona) when Yona came to him to vouch for peace between Xing and Kouka.
When I first read this manga, I was a teenager who didn't have a habit of trying to go in depth with characters, but looking at these frames now, I can say that this scene is a big tell of how Soowon sees Yuhon. He is making excuses for his father's unnecessary cruelty, even though Soowon himself, I believe, would never do something like that.
Also, chapter 221 shows that Soowon, in fact, never questioned Yuhon's methods. His father's influence on him never lessened, even after all these years (perhaps because he's been surrounded by Yuhon's supporters since, idk, forever).
He is a king. He has to sacrifice his humanity for the sake of his kingdom - that's what he's been taught by his beloved father, whom he never questioned. ("Please, let me see the board objectively" - I almost fucking cried).
So sweet is the realization that he, in fact, can't do that. He is only a human, after all, someone who already sacrificed his childhood and his closest friends for Kouka people's well-being, and I can't imagine his heart being able to take another loss.
Soowon has basically abandoned himself. The persona he and the adults around him have raised in him is "king" (according to Yuhon's ideals). I believe Soowon isn't introspective; he has been running away from his feelings this whole time, and chapter 221 was the first time he's faced them. It's very fascinating to me: he is always ready to face the consequences of his decisions, but never to face his feelings.
P.S.: I'll be very glad to receive any corrections or different opinions, because, as I said before, it's been a while since I read AkaYona, and the moments mentioned in this posts are the ones I remember vividly.