personal headcanon with absolutely no canon basis whatsoever:
In his private time Aku writes a fix-it fic of Journey to the West. The full thing. That's 1000+ pages when translated into English.
He's been picking at it for centuries. He's quietly publishing it chapter by chapter under a pseudonym. He doesn't want people to read it because Aku wrote it, he wants it to stand on its own.
"How is it a fix-it?" Okay so Journey to the West opens with the monkey king Sun Wukong—whose superpowers include shapeshifting and immortality—attempting to rebel against heaven's emperor. Emperor calls in Buddha; Buddha defeats Sun, seals him under a mountain, and 500 years later lets him out on divine parole to atone for his crimes by helping a monk travel from China to India.
Aku's mad as hell that the badass monkey yields to Buddha. Aku's years-long imprisonment in a tree made him vengeful, not compliant. And the gods have been trying & failing to kill him since before he was born, he would never surrender to them—so why should the monkey?
So he's been rewriting the story so that Sun's secretly an evil mastermind rallying all the villains and monsters he meets during their journey west, plotting to overthrow Buddha and take over reality.
It's no literary masterpiece. However it's got a small but fascinated cult following. Partially because of the mystery of its author's identity—they've been releasing a chapter about once every five years for the past two hundred years. What??
And partially because trying to decipher the author's psychology is fascinating. Like: it's extremely obvious that the author is characterizing Sun Wukong as an expy of Aku. (Aku is NOT writing a self-insert on purpose, he's just really unsubtle.) But why is someone rewriting a prehistoric epic fantasy as an allegory for Aku conquering the world? And why is the author disgusted by JttW's original narrative of atoning for hubris against the divine?
Considering that Aku has been earth's pseudo-divine eternal ruler for longer than recorded history, everyone thinks it'd make more sense to cast him as Buddha or the jade emperor. Making him the underdog on a pilgrimage is a baffling literary choice. Is the writer an incompetent hack who doesn't understand the original narrative, or are they operating on hitherto unknown levels of allegory?
(The answer is he understands the original very well—he just completely disagrees with it. And he's an incompetent hack.)
One theory is that the author wrote the whole thing 200-something years ago and their descendants have been slowly releasing it posthumously. But in recent chapters, the monkey's started to fixate on the monk as a greater nemesis than Buddha, and the monk—previously a rather flat character—has been fleshed out in an oddly Jack-like way—so obviously the author is commenting on the current political climate (though their intended message is inscrutable). The author must still be active. But how? Are they an alien? A fairy? A robot churning out very slow slop?
"Aku's the author" is nowhere on anybody's list of theories. In fact, readers kind of wonder whether Aku will execute the author for characterizing him as an ambitious primate rather than the born ruler of the world. Perhaps they'll never know.
Also—and this is very, very important—the way Aku writes & characterizes Sun Wukong is basically just Mojo Jojo.
