Chapter 119: Well, Phooey.
Since Deng Ai might not be willing to surrender himself willingly, Zhong Hui doesn't go to apprehend him directly. Instead—acting on Jiang Wei's advice—he sends his deputy Wei Guan to make the arrest, figuring Deng Ai will kill that guy instead and give Zhong Hui an excuse to march in with troops. Wei Guan ain't no dummy, though, so instead of showing up at the door and serving papers, he sneaks into Deng Ai's house at night and has him tied up.
Zhong Hui and Jiang Wei show up afterwards to get their jabs in on the captured man—both verbal and otherwise—before Deng Ai is ordered to be sent back to the Wei capital in a cage.
As the prison cart rolls off, Jiang Wei asks Zhong Hui, so, what are you gonna do now? I mean, if you think about it, you now have control of a hell of a lot of Wei forces... you have control of me, the guy who has the loyalty of all of Shu's old troops... you have a base of power here, with easily-defensible mountain passes... and there's a lot of examples in history of guys who had what you have now, didn't seize their opportunity, and ended up paying for it, so like, I'm just saying...
Zhong Hui didn't really need the convincing. But to really solidify matters, a couple days later, he gets the letter that Sima Zhao had sent telling him he was bringing his army to help him round up Deng Ai. Jiang Wei goes, look, he knew you could handle Deng Ai yourself. If he's on his way, that means he's moving to handle you.
So Zhong Hui figures, all right, let's start the revolt then. Maybe he takes over Wei; worst-case, he stays in control of Shu for a while and keeps the whole three-kingdom thing going.
(THIS was the reason Jiang Wei surrendered to Zhong Hui last chapter—his last-ditch plan. Befriend Zhong Hui, take Deng Ai's troops, re-form some iteration of Shu, and surprise Wei.)
To make it seem like he actually has a legitimate reason for revolting against Sima Zhao, Zhong Hui lies and tells his commanders, hey, remember how Sima Zhao had that one emperor killed back in Chapter 114? Wasn't that messed up? That's why the emperor's mother secretly ordered me to get rid of him!
The commanders aren't entirely convinced by this, but go along with it mostly because they don't know what else to do. Jiang Wei realizes the commanders aren't as thrilled with the plan as he might have hoped and tells Zhong Hui to just kill them off, and Zhong Hui goes, yep, I totally intend to do that! And then he just has them confined to the palace instead for some reason.
Well, of course one of the commanders is able to slip a message out to deputy Wei Guan, informing him of what's going down. He marches in to put a stop to the rebellion, coordinating with the commanders on the inside, and Zhong Hui basically has no chance. In the fighting, he's struck down by an arrow; Jiang Wei, suffering pangs in his chest that leave him too weak to fight, takes his own life.
With a lot of people who were loyal to Deng Ai suddenly free from Zhong Hui's makeshift prison, Wei Guan goes, shit, one of those guys might go release him, and he'd probably be mad at me for arresting him. So Deng Ai ends up quietly assassinated before he ever makes it back to the capital, and Wei Guan is put in charge of Shu before promptly disappearing from the rest of the book.
Thus, the victory against Shu is complete. And to showcase what a shitbird Liu Shan is, he goes to Wei to party with Sima Zhao and is entirely unable to shed a single tear for the kingdom his father built.
Well, at least Sima Zhao condemns Liu Shan's favored eunuch Huang Hao to "a lingering death on public ground", so there is some justice in the world at least.
After Sima Zhao's great success in overtaking the Riverlands, emperor Cao Huan names him the King of Jin (as though he had any other choice in the matter). There's a brief interlude where everybody is watching with bated breath to see if Sima Zhao names the younger of his two sons as his heir and spawns a massive succession crisis, but at the last minute he does the smart thing and decides his older son will be heir instead. Then he has a stroke and dies, leaving Sima Yan to become the new king.
Sima Yan wastes no time in going, "Hey, wasn't Cao Cao's whole bit that he did a lot of cool things and basically paved the way for his son to usurp the empire? Well, MY dad did a lot of cool things too, if you happen to see where I'm going with this..."
Jia Chong—the guy who had been pushing Sima Zhao to take over like ten chapters ago—totally sees where he's going with this, and persuades Cao Huan to abdicate his position. Sima Zhao does at one point use the excuse "hey, this is just payback for what Wei did to the Han!", which, sure buddy, whatever helps. Either way, he's the emperor now—no matter what anyone says—and only one guy gets beaten to death with a ceremonial golden mace in the process.
With that, the Jin dynasty is established, meaning that the kingdom of Wei, too, has ceased to exist. That means there's really only one last place to turn our sights toward now; and rather conveniently, there's also only one last chapter in which to do it.