Liu Bei is the "protagonist" of the RoTK, his main trait is he works with anyone to oppose Cao Cao (except when he takes refuge with Cao Cao) but he took so many Ls that tub thumping could be about him.
In this case he leaves Cao Cao's service to serve Liu Biao, who supposedly wanted to leave Jing province in his hands
That's a throwback right there, I'm pretty rusty myself which is why I ignored the Biden section. Old men going on poetic (and useless) tangents was really common, from context I assume he is Cao Cao