Actually, now that I think about it, something doesn't quite make sense here. King Il, as Yona's father, kept her identity as the CDK reincarnation a complete secret from everyone except for Soo-won. It appears as though he was bragging or boasting about this fact to him in the flashbacks, which would make sense if he was still religiously devoted to the CDK faith in secret and wanted to rub this fact in his brother/nephew's non-religious faces. Sort of like an,
"I was right! I told you so!" kind of moment. This chapter, especially, made Il seem like he was somewhat jealous of his brother for holding a more direct connection to the CDK lineage through his marriage to Yon-hi when the reality is that the future end results turned out completely different. Because Soo-won was born as a normal CDK direct descendant, but Il's own daughter Yona was the true reincarnation of the CDK. Also, it feels a bit strange that if Il was still secretly practicing the CDK faith, why did he choose to not place his daughter on the CDK pedestal and instead make absolutely certain that no one knew of her real identity? In this type of situation, to me, it looks like Yona's father was in actuality a dark two-faced character? Like how Yona remembers her father as a gentle soul, but Hak recalls a moment where he showed a stronger type of nature; that incident where Il grabbed Kan Tae-jun's blade when he was trying to force Yona to go with him. Honestly, I have this sinking feeling that the whole core point of this arc that Yona is reading about, is to break her previous illusions of how she once saw her father and learn the truth; that who she thought at the surface was her father wasn't all there was to him. I mean, that's kind of been the biggest question Yona's always had throughout the series. That she couldn't understand why Soo-won would murder her father when in her mind, Il has done nothing to deserve it. Sure Yona has witnessed how some of Il's misguided policies have badly affected the country overall, but none of that would really warrant murdering the King in her eyes, unless there was a deeper and more personal reason to kill him. I think this arc is going to help reveal the true corruption hiding within the royal palace surrounding both the CDK religion and how her father was a greater part of it. Especially if, Il had anything to do with his own enthronement by using his father's religious devotion to the CDK faith by stating his daughter would be the next reincarnation of the CDK. The plot thicken and I'm longing for the next chapter!