This is actually quite unbelievable and too quick for finishing things at Juuko.
I actually think this is flawlessly consistent with how we understand optimal tactics to function.
You always want to eliminate the “brain” of an army first. At Bayou, Ouki’s tactics weren’t focused on eliminating Houken, it was Fuuki and Chou Sou that he focused on slaying because they were the brains behind the Zhao. And remember, Fuuki was slain on day one of that battle, and then the Zhao immediately knew that Ouki’s next target would be Chou Sou and did everything they could to protect him.
At Shukai Plains, Ousen remarked that the Qin right wing had made a mistake in their plan to slay Gakuei, and that they should’ve actually focused on eliminating Chou Garyuu because he was the brain of the right wing army.
You need to take out the brain first. Tou killing Juukou Ou this quick is just good warfare lol. You don’t want to mess around and fight a big prolonged war in a situation like this, and with Juuko Ou dead, I think it’s pretty safe to say that the Chu are finished unless they can even the odds by slaying Hou Mei
and Mou Ki which...yeah that won’t happen lol.
This is the point where the Chu will start to fall apart and it’s because of Tou Sama
Unless Moubu dies to Man’U of course lol. But that won’t happen either.