I always thought the shield and sword was Yoon(shield) and Hak(sword). I guess I have to keep reading to see if my assumption is correct.
I think you may be right (and it would be awsome). But I personnaly think that if Hak is indeed the sword, then Soo Won is the shield, or maybe it's the other way around.
I decided to read the whole story once again, and I fell upon this sentence from the White Dragon, on the 18th chapter : "Could his (Hak's) strength almost be on par with the arm of the Dragon ... ?!" ( http://www.mangago.zone/read-manga/akatsuki_no_yona/an/akatsuki-no-yona-chapter-18.html/22/) ... And well, Hak has proved thousand of time that he is, indeed, as strong as any of the Dragons, whom possessed advantages. And everybody says, all the time, that his strength is surhuman. For example, when they fell of the cliff at the very beginning, Yoon says that he should be lying on the bed, almost dead, and instead he's up, playing with the Princess. And when he fights with the White Dragon for the first time while being armed by his previous fall, they're all amazed that he is still able to fight like a god, like a Dragon, whil being this hurt...
SO. I think he's the Shield of the Princess, and Soo Won is the Sword. Hak protects her while Soo Won prepares the path in order to let the Princess reign in a peaceful Kingdom. As he said to the White Dragon, his goal is not to be the King.
I still don't understand why he killed Yona's father, but in one of the early chapter (before the 18th), when we saw them while they're still childrend, he's almost crying when Hak told him "you have to marry Yona, then you'll be the king and we'll be together forever". He almost cried and thought somthing like "When this time come, I know that you and Yona won't be by my side" ... So it's something that he had prepared for a long, long, long time.
... Anyway, I just wanted to say that I think you're (partly) right !
I made that comment when I was around the 40th chapter. Plus I was watching the anime. There was a scene where Yoon was carrying a shield. I already knew the part about Kija thinking Hak's power could be on the same level as his dragon arm.
But considering the latest chapters, I wouldn't be surprised if Soo won and Hak were the shield and sword. Considering how well their teamwork was when they saved Lili. In fact, Hak and Soo won would make more sense. I remember Ik Soo saying "the sword and shield aren't ready yet".
And here ! Hak says "I'm a human shield" ( http://www.mangago.zone/read-manga/akatsuki_no_yona/an/akatsuki-no-yona-chapter-27.html/23/) ... Well, I think he just says it because he works as a bodyguard but I don't care, he said it !
It would be really awsome if you were right !
Let's face it. We're not expecting Soma to win at all. Maybe a tie. Maybe Soma loses and learns from central, challenging them again when he's ready. But I'd be interested to see what would happen if Soma did win. The author still hasn't disappointed me.
This is true fact. Guys read it.