I suddenly remembered an idea I had eight hundred years ago: a deceitful yet devoted top, and a principled yet selfish bottom. Sure enough, all the ideas I had eight hundred years ago featured an older top...
Basically, the bottom is the son of the leader of the martial arts alliance. A few years after his father dies, he goes down the mountain to restore the alliance's reputation and runs into the top, who has countless ties to his father's death.
When he was young, the top was a passionate disciple of a prestigious orthodox sect, but he fell in with the wrong crowd and defected to the demon cult. (Sad.) Anyway, after one thing and another, his martial arts were completely destroyed. Ha ha. Now he's a wheelchair-bound invalid who can't tell the truth to save his life.
The bottom is a little wary of the top's identity, but he's an upright sort. The top acts all pitiful and puts on a show of helplessness in front of him, so the bottom sticks up for him, saying, "Don't discriminate against him. That's not how people from our prestigious orthodox sect should behave."
And that's how the top gets to throw his weight around. One dares to lie, the other dares to believe him, and before you know it, they're practically a married couple. I can't say more or I'll spoil it.
That's the blurb for now. Maybe I'll polish it into a proper period-style blurb when I have time.
Theme: Stay true to yourself and remain unmoved.