thank you <3!!
Yes I think hearing from Rapa helped Suwon see the bigger picture a lot! I don't think he's willingly trying to act against the Yuhon faction and it's more that well, they're done for so no need to worry about them anymore. Like a weight off his shoulders. I find it particularly interesting they were partly defeated by Kija in a chapter where he also "goes against" his predecessors in a way, even if Kija never saw them as a shackles he has to go against. Kija is able to naively and purely assert his own will over the souls that could burden him, to let go of them for his friends in the present, so it's poetic that by echo it freed Suwon from his chains of carrying a legacy as well.

I wouldn't really say Yuhon faction are fueled by revenge, but they are resentful, yeah. I think they genuinely believe what they're doing is right and they just can't get over everything Il represents and the symbol of making his daughter the next ruler, and that they're frustrated by it. More than revenge, it's the stubborness to follow strickly what they think Yuhon would have done. What they don't like is Suwon (or Keishuk) changing and acting differently, assuming they're losing their way under Yona's influence, similarly to Yuhon's reason for killing Kashi. Attacking and killing Yona and the dragons now is stupid and in no way benefical to Kouka, but they're unable to move on from Yuhon's death basically and I can't completely hate them for it either. If you have the occasion to check the volume ver of chapter 252 someday I recommend it, bc it adds panels of sohga and yona's faces here and there and you can see Sohga looks genuinely upset and pained at the idea of Yona succeeding Suwon and I think that's just...yeah. Idk it reminds a bit of pre-castle arc Hak, it's about the things you can't overcome and can't accept no matter what. That doesn't excuse them at the end of the day they're not very deep or whatever but well, they're still kinda human.

I think you sent me this ask before ch262 anon, but the latest chapter also gives Suwon's reactions in ch256 a new flavor. Suwon was accepting Shinah's attack and his own death as punishment. Yet he still didn't die. Upon waking up he immediately claims that no they won't retreat and he has to keep moving forward no matter what even if he dies in Kai. This is Suwon punishing and harming himself in a way. He doesn't deserve to breathe and to rest, he doesn't deserve to go back home when he has not accomplished his goal yet, he doesn't deserve to see Yona and Hak again after how they helped him and how he "selfishly" uses them again. He has to shut off his heart and only achieves his role and his duties, the way Yuhon's faction encourages it. Then he hears Rapa's report, and that's the reason why he realized that he was being too impatient on top of knowing Yona will definitely come back for Yun. We can't really tell how much Rapa told Suwon (like Rapa visibly omitted the part where Sohga reveals Suwon wants to make Yona the next ruler? has he even heard it???), but Suwon has been struggling since the beginning of the war notably with Geuntae with adapting to the changing and conflicting expectations of the people around him caused mainly by Yona. But it's precisely thanks to people changing around him, challenging the ideal Yuhon represents and that these characters used to aim for that Suwon can in turn change as well. The shadows were the only ones still clinging so hard on it in their inability to move on. The vow they made to Suwon 10 years ago is about protecting him...but it's actually more about protecting the image of Suwon they want and that they force on him, making him unable to change despite the different circumstances a decade later. On the other hand, Hak let go of his own vow to Suwon that he also made 10 years ago and trusts what he knows of the Suwon of the present and that's how they can change and work together today.

Also yeah the fact this faction is called "the shadows" says it all to begin with. But Suwon now lost the shadow of his father's legacy and the pressure that comes with it now, he doesn't have to be his replacement, there's no one left that even asks for it, he can just be Suwon, the rational King who also loves people and who deeply cares for and trusts Yona and Hak despite all odds. Of course there's still some way to go, he still forces himself to act as a King in front of the people until he dies, he still accepts his death (that 100% won't happen just to be clear), that he's replaceable and that he still has to dedicate what's left of his life to protect Kouka...but that was a first step, and I remember ch256 gave me the assurance that this decision of Suwon will probably open new doors for him to live in the end. Actually it seems that this too is fate? And I'm not sure where it's going with that but wait and see...
Thanks for the ask!! Seeing it as Suwon going against them is also very lovely and that's close to how I see it, on my part I just assume that there is no one to really go against anymore since the shadows are probably either dead or will never return to the picture at all lol.