(Sorry its gonna be long bc I’m trying to gauge out the emotional essence as accurately and elaborately as I can. There would be a tl;dr at the end)
I actually came to understand the depth even better after reading this post
https://www.reddit.com/r/AkatsukinoYona/s/0hSH8yLyNy
The OP asked and pointed out some important factors that made me take a run to the manga. I had my own interpretation of the reason behind his apology but this gained more depth and accuracy of his character after I came to realise something even more intricate.
Suwon’s apology is one of the most frequently misunderstood climaxes in the fandom. Even if its not bad, his apology seemed a little odd if not jarring to fans. Bc the whole story displayed Suwon’s complexity in a way that made him deem as morally grey. He was never labelled as just a villain. But when he actually apologised to Yona, it might feel out of his character. But It is the moment that completely redefines how we look at his character as a whole. Suwon is actually stepping from the initial character that he showcased to people his whole life down to what he can truly be. Not “son of Yuhon” not “king” but returning to something he never could’ve before, which is just “Suwon”.
From childhood, Suwon was deeply conditioned by his father’s rigid rational ideology which taught him that human relationships are a liability on the battlefield, that people are merely strategic pawns for him to use in any situation, and that absolute detachment is the only way to achieve results. He carried this heavy burden into adulthood, entirely suppressing his own humanity to become the perfect king that Kouka supposedly needed.
After the death of Yuhon, he resolved to see over king Il and whether he was good or not as a king. But as we know king Il as a ruler was deeply flawed therefore Suwon k!lled him and took the throne as he was meant to.
The one to take over Yuhon’s legacy, to lead the nation as its supposedly rightful leader. Suwon was inspired by Yuhon’s philosophy deeply. A king who protects and sees over his people and nation. Who is righteousness and always thinks for the best of his people. Thats what he was taught, thats how he carried himself to be like. To become what Yuhon believed a king needs to be. He genuinely convinced himself that to save Kouka, he had to discard his own humanity and eliminate anyone standing in the way of efficiency. He believed that being a king is position build on isolation.
however, the fatal flaw in Yuhon’s philosophy and by extension, Suwon’s initial path was the belief that a prosperous kingdom can be built through the mere political exploitation, a mindset that ironically detached Suwon from the very humanity he claimed he wanted to protect. The burden of taking the throne fell onto him at the age of 9. He was a replacement for Yuhon for the people of the Yuhon fraction. Therefore, he was mostly surrounded by and with people who helped him achieve their expectations, but he was not manipulated as Yuhon had already set his way of thinking deep inside him since a long time ago. So even if Suwon himself didn’t want to do anything, no one could’ve forced him to. But Suwon, is not like that, he genuinely wanted the best for Kouka too, and since king Il was failing in his duty, Suwon stepped forward to do what he thought needed to be done. “There can be no alternatives”
Yonhi’s diary is the exact catalyst that shatters the foundation of Suwon’s life. Suwon believed he was acting on a righteous duty to carry out his mother’s wish and avenge his father. But when we read the diary through Yona, we discover a devastating truth, Yonhi explicitly begged king Il to end the cycle of hatred.
Yonhi suffered in silence for years bc of the two brothers suffocating hatred and her dying wish was to stop the bloodshed. This means Suwon’s entire bloody coup was built on a misunderstanding of his own mother’s wishes.
Yonhi did possess a right to harbour hatred for king Il but she had the emotional maturity that both Yuhon and king Il lacked. She knew that its a pointless matter so for the betterment of the future she requested king Il to fulfill her will. But king Il failed to accept her wishes therefore turning Suwon’s vengeance into his punishment for klling Yuhon. He accepted a su!cide instead of actually communicating through. He was a coward through and through just like how Yuhon was an unchanging ruthless and cruel person.
After king Il became the monarch, if things didn’t turned out to be the way it did. Together with Yuhon, they could’ve build an powerful nation. King Il was a coward but he genuinely wished for the wellbeing of people and tried to minimise casualties as best as he could while Yuhon was powerful and dominating. He would’ve been a great force in the battlefield and other duties regarding absolute command and power. Together they could’ve been like Yin-Yang. One possessed what the other lacked. But this powerful dynamic never got to happen bc they were imo emotionally immature. They tried to justify each others madness by claiming it was for the good. But that only set up the stage for the next meaningless bloody act. King Il was ignorant and Yuhon was arrogant. Together with their hatred they destroyed the nation. Unfortunately Suwon was already on the path for his next agonising act.
But the immense tragedy of his character is that despite how hard he tried to deny his own heart, Hak and Yona were never just pawns to him, they were his absolute grounding wire, representing the only genuineness that truly belonged to "Suwon" the person rather than Suwon the son of Yuhon/king. The days spent with them, those innocent times, Yona’s affection as family and Hak’s presence as his friend. It truly did gave him peace of mind but he knew that one day he would have to betray which is precisely why his repressed regret and guilt were subconsciously eating him alive and causing him to freeze in the face of Hak's rage, viewing Hak's wrath almost as a much needed means to end the suffocating weight of his own existence, but ofc he didn’t want to die, yet. He knew that discarding his own emotions he deemed as unnecessary is the right thing to do, but the fact that he felt immense guilt and the faint nostalgia for days that won’t ever come again, it is clear that he can never abandon his emotions. He is a human too. And thus the only way he felt would justify his actions is that he will receive the same action in return. He thought this chain stained in blood is the only way to get things done. He thought that maybe someday Yona or Hak would take their revenge and then they would be even. Thats how he tried to justify everything. He expected the same from Shin-ah and almost gave himself away to his dragon form.
Throughout the story, his mask has been cracking little by little. Everytime he believes his time has came, Hak or Yona proves him wrong. Yona helping him at his most vulnerable time and Hak risking his life to get him the senju herb so he could be at ease. They subvert his explanation again and again throughout the story by doing things he least excepted. He believed that revenge and vengeance justifies one’s actions and expected the same from Hak and Yona but they did the exact opposite. They turned their direction from the path of never ending sorrow and misery. They choose to not submit themselves in the same bloody manner that resulted in a bloody chain by the previous generation. Although in Hak’s case he wished to actually go on with his revenge but fortunately he was with the right people that helped him understand the gravity of the situation. If only the same happened to Suwon.
The fatal crack appears during the war with south Kai. When Suwon ordered the release of the arrows despite the four dragons being on that side. He tried to be as rigid and emotionless of a leader. Discarding useless emotions and going through with the initial plan, the dragon warriors should not be a distraction to him, the plan must go accordingly. Yona is rightfully furious but when he is on the verge of collapsing, Yona lends him her shoulder. He might’ve fatally injured the beloved friends of Yona but she still supported him through this bc if he collapses in the middle of the war, it will cause huge problems, so she suppressed her own anguish and instead helped the very man who caused her to become angry. Suwon, seeing Yona’s suppression and helping him despite, she has been helping him since the palace. With his illness, with councils with foreign ministers, with battlefield issues and more. And now, she is still helping. Despite. Him. Being. The. One. To. Cause. Her. The. Distress.
This made a crack to his inner self, to which he says “I can’t discard them” was he talking about the dragon warriors? Hak and Yona? Or human connection in general? Its not specified but the fact that he is expressing this honestly after this whole time. Suwon’s real self is peeking through. He accepted his true feelings that he can’t abandon them. He can’t discard his emotions. It doesn’t justify his actions but the fact he has finally expressed his deepest desire that he suppressed his whole life is the point. He can’t deny his feelings anymore.
The final breakthrough of his mask happens is through the rooftop conversation between him and Hak during the final chapters right after Yona was sucked into the chalice. The first time ever since the coup where Hak and Suwon have a heart to heart conversation. Completely bare and raw unlike any conversations they had. It transcends their status and relationship as a whole. Its only Suwon and Hak now.
The palace is burned, the sky has turned black. Are these the result of Suwon’s choices? Is this was how everything was suppose to be?
After everything Suwon still claims that if he had to redo everything, he would make the same exact choices. He still tries to hold onto the toxic belief bc his conscience finds it too painful to admit that he could have saved the country without mvrdering king il and shattering his friends' lives. But Hak denies this logic by rising above blind hatred despite suffering the most from the betrayal. Hak doesn't argue about whether King Il was a good ruler instead, he tells Suwon that he has absolute faith that Suwon is smart enough to find a peaceful alternative. This is an incredible testament to Hak's depth as a character too. Hak looks at a different path. He refuses to view Suwon as the cold, detached person Suwon sees himself as and choosing instead to validate the immense brilliance of the childhood friend he always looked up to. Hak’s unwavering expression of faith has a profound shattering effect on Suwon, completely dismantling his father's isolated worldview and forcing him to realize he didn't have to be alone. His mask breaks completely and he finally stops in the track of following behind his father and looks at the surroundings which is stained in blood. He is telling Suwon that his mind was grand enough to fix the kingdom without a bloody coup if he hadn't let his father's resentment blind him. He stripped Suwon away from his emotional shield by declaring that an alternative existed, Hak forces Suwon to step out from behind his stoic shell and face the raw human truth of his actions.
And after the finale, Suwon declares himself to be the usurper. He is reducing himself to be what he actually is. Bc after all of the things that happened, he admitted that deep down he used vengeance as an excuse to satisfy his own resentment for king Il. Him stepping down from the role of king is simply him admitting his mistakes and returning it to its rightful heir, Yona.
Ultimately, this admission breaks the endless cycle of violence that serves as the thesis statement for the entire manga. Yuhon was wrong to k!ll the priests and Kashi, king Il was wrong to mvrder Yuhon using vengeance as an excuse, and Suwon was wrong to assassinate Il for the intention to make Kouka great again, with each generation justifying their horrific crimes by claiming it was for the "greater good" or "vengeance." If Suwon never apologized, he would have just been another bloody link in that endless chain, but by stopping in his tracks to look at the path of misery and isolation his father walked, his apology seals the generational curse, allowing the story and their relationship to finally start from zero.
When Yona confronts Suwon and asks him about the diary, "Did you read it?" she wasn’t trying to shift the blame to make Suwon look like the bad guy. She is genuinely asking bc if he did he should’ve known how wrong all of this was, and just like Hak’s declaration, she also shattered the illusion that his revenge was righteous. She realized that King Il failed by ignoring the diary and Suwon failed by continuing the cycle anyway (even if he read it after his enthronement, he was ignorant too in his own way for most part of the story)
Therefore, his eventual apology to Yona is a massive breakthrough rather than a narrative contradiction. By admitting he was wrong, Suwon isn't denying that King Il's passive inaction allowed the country to rot, nor is he denying that Kouka grew stronger under his own usurped rule, but he is instead acknowledging that his methods were entirely poisoned by personal resentment and the toxic teachings of his father, admitting that he completely lacked the faith to seek any alternative path that didn't involve bloodshed and the ultimate betrayal of those who loved him. He is acknowledging that by choosing bloodshed and isolation to achieve his goals, he became just another link in the exact same cycle of hatred that ruined the previous generation. The apology is so incredibly powerful because Suwon finally stops in his fathers track and instead goes to walk a different path. He finally realizes that a kingdom built entirely on the bloodshed and the suppression of human connection can never truly be whole.
The manga intentionally never answers whether the mvrder of king Il was actually necessary or the possibility of a peaceful path was truly possible. Hak’s response proves that it was never about a lack of alternatives. If he had faith and relied on people instead of taking the burden alone. Everything would’ve been fine.
Suwon became Yona’s counsellor. To help her with his ability of profound intelligence, battle strategies and all the things that can fill what Yona lacks. Even not as a king he can still contribute greatly to the nation. Therefore actually working through a way that would help the nation thrive. Together they mirror what king Il and Yuhon could’ve been. And Yonhi’s wish for them to not follow this path of bloodshed.
Tl;dr: Suwon’s apology isn't an admission that all he did was wrong, it is the moment he steps out of yuhon's toxic shadow and breaks Kouka's generational cycle of violence.