There are so many issues with this classic all of which can be blamed on its 90s dated style.
For instance in hindsight, in chapter 1 Kyoshiro allowing himself to get roughened up so much by some everyday thugs that Kyo shows up is laughably irresponsible on Kiroshiro's part by the time you read the final reveals.
And you know it's because in chapter 1 if the at-the-time unclear set up was Kyoshiro can't help it he is weak but he's sealing a super powerful guy inside him then no problem that's a common premise. But then you throw in the twist that he is actually much stronger than Kyo and always has been and there isn't an artificial limiter or anything at any point then it all falls apart.
Also in the earlier chapter the characters keep whispering in Kyo's ear "I'll take you to that person" who are they talking about? Later on the first big bad was Nobunaga so we thought they were talking about him obviously, but then that guy was a red herring and the final big bad is Crimson King so what was Kyoshiro and Kyo looking for in Edo?
Even though on paper I absolutely LOVE the OG premise:
-A war that changed the world happened 4 years ago.
-There was a legendary samurai during the war.
-He disappeared after the war, end up in the body of some weak guy. Weak guy may knows what's going on, he may not, legendary samurai fresh out the water because he was sealed for 4 years.
-All the power players each with their own agenda are surveiling this weak guy just waiting for the moment the legendary samura resurfaces
-Then we have our fresh new girl who doesn't know anything resurfaces him, and the story kicks off as we learn alongside her and him the new world powers that be each try to manipulate the legendary samurai as he searches for his real body.
Such good set up in the beginning, Okuni Tora Yukimura all with unknown motivation but all seems to know something Kyo doesn't and they're trying to steer him for their own benefits with the promise of giving Kyo what he wants, and since Kyo just woke up 4 years later not knowing anything he has no other real options.
Too bad it didn't exactly turn out that way beyond the forest arc.
Okuni and Tora didn't go anywhere, Okuni who was straight up introduced as the 2nd main character was completely absent by the last 1/3rd.
Sakuya wasn't that important despite being kept super mysterous for 2/3 of the story.
Yuya's brother killer hunt not that important overall, you knew it was going to be Kyo or Kyoshiro but then also know he's either innocent or had reason to do it.
Only Akira got any sort of purpose in the story. Hotaru and Akari can do without, Bon completly pointless as a fighter or plot point.
Kyo's 4, Nobunaga's 12, Yukimura's 10, the former crimson king (what difference does it make if he's simply the current crimson king)'s 5 shining stars and 4 elders. You think that's enough squads/bosses?
The entire manga can litearlly be summed up to guys fighting guys who takes sequential turns progressively power up mid fight for 300 chapters.
So really good set up for not enough pay off ? I agree.
I also agree that for all the talk about Sakuya, she was in the end nothing more than a plot device that has linked everyone else (Kyo, Kyoshiro, the former crimson king, her brother, etc)
And in general women characters in the story do not get good story arcs in that manga.
Also the manga suffer from power creep : when you have characters that powerful you can't put mobs before them to fight, and that explained to me the too many number of squads and bosses and set up hype before their battle.
But I always thought that story was a character driven story rather than a plot driven story, and drive the story thèse characters did.
You have more recurrent characters than Naruto yet most of them get their entire character arc story done by the end of story. (RIP, the story arcs of Bontemaru and Okuni)
As you said, they each have their on agenda, move for them, and all their interaction are humanly believable and fun. I remember that story yesterday while sadly realizing that 2 decades after it, we regress and a lot of manga do not even come close in character consistency through their ordinary behaviors and dialogues.
Pretty sure BeniTora's overall arc was his conflicting feelings about his father, he hated his methods and so seek independance, but couldn't prevent himself from admiring him. By the end of his journey as he became a better and more experimented fighter he managed to understood him, and that why he became his succesor.
Akari story was not fully commiting to her (I know he is born "him", and I will still call "her" without caring) on life : she has what she want people and friend she loves like family, yet until her reveal she never fully commit with it believing it was like à dream she would have to wake up someday.
Hotaru was just vibing the all story. But in his fight against his master, he reaffirm himself, realizing all journey he went through by looking back being satisfied with it.
And Kyo's story arcs was what you summed up in your last paragraph, but from what that same character said about it (speech about his scars in volume 36 if i remember right) he is fully aware of it, fine with it and find meaning in it.
The all story is people fighting, and each time growing through them for the ones surviving it.
For me that point came across hard during the final fight between Kyo and Nobunaga. Nobunaga was the only one who didn't grow and even possibly mentally regress between the 2 fights and the results were clear.
Thank you for reading all of this.