An elongated version of how I think Hara will write the final Chu war with reference to history:
So Shouheikun will ofc be the King of Chu, Hara has begun setting this up since Shunshinkun’s assassination and Kou Retsu’s death. Chu is craving strong leadership right now.
The Chief will lead Chu alongside Great General Kou En, who is debatably the most hyped General in the entire manga, with abilities above that of Kanmei. Kou En has stated that he believes Chu is not taking advantages of all of its natural resources, but this will change under King Shouheikun, who is a King rivaling Sei in strength, and who’s only mission in life now is to stop the Qin from unifying China.
So ofc, Sei consults both Ousen and Shin and goes with Shin’s plan, Shin leads 200K men into Chu and is essentially baited deep into Chu territory, before the combined strategies of Shouheikun and Kou En are suddenly executed, with Kou En revealing a 500,000 man Chu army that he had intentionally concealed, which utterly devastated Shin’s army and kills many commanders that we have been with for years in the manga (Denei, Denyuu, Garo, etc etc).
However Shin, who has been the type of General to face his opponents head on, uncharacteristically calls a retreat which ultimately prevents his army from being engulfed and exterminated in Chu.
Shin will have taken a devastating L at the height of his strength, after he has assisted in the overall unification of China, helping Ouhon conquer Wei among other feats.
Sei realizes that to defeat Chu, he will need the full might of Qin and the new 6 a Great Generals, so instead of demoting Shin, he persuades Ousen to lead an army of 600,000 lead by all of Qin’s New 6, with Ousen as their leader.
Ousen at first baits Shouheikun and Kou En by bringing his entire 600K army to the Chu border but then ordering all forces to hold. He deliberately makes Kou En and Shouheikun think that he intends to fight a long war of attrition, and a few weeks pass by as Kou En and SHK hold on place, contemplating how they should defend against a prolonged war with Qin.
Just as Shouheikun and Kou En begin to change formations to plan for a long, attrition style warfare, Ousen suddenly orders a full 600,000 man charge into all out war. While giving off the impression that he planned to fight a long-drawn out battle, Ousen was secretly training Qin troops behind the front lines to fight in Chu territory, his true intention being to utterly crush Chu with brute force the instant that they began moving their forces around in a way that that left them open to a brute force attack.
The result of this charge utterly devastated the Chu to such an extent that Shouheikun personally grabs a Glaive and heads to the battlefield. Ousen is using a two-pronged assault with Moubu and Shin at the center, Moubu’s unrivaled strength as well as Shin’s newfound determination to make up for his previous blunder makes them a devastating force that the Chu cannot stop. The ferocity of Shin’s assault is so incredible that Renpa personally picks up a Glaive and rides out to face Shin, and yeah. That happens.
After Shin slays Renpa, it is made clear that Shin’s target is none other than Kou En of Chu, the greatest in all China and the general who devastated him the year prior. Kou En is no fool and falls back to a Chu city (forgot the name) placing between he and Shin his strongest defensive formations, formations befitting the strongest tactical generals ever. The rest of the 6 GGs bar Moubu and Ousen himself join Shin and opt to slay Kou En, as finishing him should finish Chu.
With the help of Mouten, Ouhon, and either YTW or Kyoukai, these defensive formations are overcame with difficulty and Shin makes his way into the city where Kou En will make his last stand. Shin comes face to face with Kou En and to his shock, Kou En picks up a Glaive and proceeds to royally rock Shin’s world. On top of being an incredible tactician, Kou En’s martial strength is on par with the strongest warriors ever, befitting the Supreme Commander of Chu and the Conqueror of the East. Surpassing Kou En is something that could only mean that Shin could be considered the Greatest General of all time. So ofc after a brutal battle, where both Kou En and Shin recall their close brushes with death and their years of incredible battlefield experience, Shin slays Kou En which should effectively mark the end of the battle.
However, a large portion of the Chu army continues to fight, their strength now seemingly amplified as Shouheikun, the Last King of Chu, personally joins the battle. The strength of the Chu soldiers under their King, and the last hope of the state of Chu, rivals the same miraculous strength that Sei conjured from the people of Sai. It’s as if that same miraculous strength that saved Qin has now been turned against them, as Chu makes one last effort to save themselves from “destruction”.
Shouheikun tears through the battlefield with complete ease, intent to slay Ousen. Before he can reach him though, he comes face to face with Moubu. Read Hara ‘s SHK vs Moubu short for more details. Lol
Long story short, the strength summoned by SHK against the overwhelming odds of Moubu is terrifying, and after a grueling 1v1 duel, Moubu emerges the victor, which ends the battle for Chu.
China is now officially unified, though maybe Hara will establish that Ousen has spent years secretly taking steps to raise his own army against a unified Qin or some shit, and Ousen will be the one to lead the final Qi army against Shin, truly solidifying Shin as the GOAT as he defeats Ousen who defeated Chu and Zhao, but I doubt this will happen lol.