I think that some aspects of the story we're added as the chapters kept coming out as the author said the story was supposed to be even shorter and at the end some things don't make sense completely. Also the story is not told in a linear way, using a flashback.
Yu Lang killed the emperor on their first life, it was their original meeting.
I took the story of the serpent and the swordsman as a legend within the story (distorted by time) or as one of the "betrayals".
And that Yu Lang and the monk keep appearing could be attributed to "magic". Yu Lang is a demon (a god) so he could do a lot of things I guess , like keeping more than one form and bodies.
I don't know if this helps you because the story IS confusing.
So, I got that the seme know he couldn’t trust the bottom, so the whole manga is a bottom punishment arc and revange loop that repeats infinitely. Because the bottom is greedy and wasn't change, a figurative Beast.
The seme kinda has a collection of the bottom skeletons in his attic. Because he can't forgive the bottom. And there is maybe where the story like lost me.
I'm so confused. The back story also has no logic.
Like, ok the bottom and the army killed the serpant, therefore the whole coffin corpse thingy.
But in reality, the serpent didn't die and killed everybody, so where does the seal, coffin and corpse come from??? Did the army kill the serpent during the tributation we didn't see and the serpent got reborn via the Emperor body as a god or something. That's why the seme got two bodies? But than it still makes no sense that there is a coffin and a seal. Who sealed/ killed seme, because the monk got turned into a puppet/ lure after becoming snake food. Also, where does the mansion come from???
I also don't get the part of nine skeleton vs. nine generation if the loop continues and they said the seme is immortal and there seem to be a 10th.
So confusing. So confusing x 100. But I liked it, I guess. Hoping for bonus chapters.<3