I’m the strongest boss

Li He is the protagonist of a novel. He kills the demon king in the tower the end.
Lin Fang 2.0 is someone from the modern world. He transmigrates into the body of Lin Fang 1.0 with his memories of his previous life.  Because he transmigrated, it causes a butterfly effect, eventually leading to the demon king to blend in with humanity and become their """"savior"""".
Lin Fang 2.0 is h*lla sus so they make him drink an elixer that cleanses the soul, leading to the revival of Lin Fang 1.0 in his own body (only for like 1 hour tho), allowing Lin Fang 1.0 to write a message to the savior (And defenitely not demon king) which tells him about the protagonist and the novel and all that jazz.
Then the """"Savior"""" and Lin Fang 2.0 go into a dungeon with one of the holy artifact fragments, in which Lin Fang 2.0 leaves the """"Savior""""  with a bunch of demons. The demon king (and defenitely not savior) goes and attacks Lin Fang 2.0 which creates a rip in his mind big enough to allow Lin Fang 1.0 to have his spirit manefest.
Lin Fang 1.0 and 2.0 talk a bit before 1.0 kills himself along with 2.0, but not before destroying the contract of the holy artifact fragment, allowing the savior (and not demon king) to take it.
Li He now gets introduced to the story and he has a system that makes him stronger. He is all edgy and shiii so he doesn't want teammates, but the system forces him to be teammates with the """"Savior"""" which dominos into the demon king winning and Li He GOING BACK IN TIME to stop Li He from listening to the system that tries to help him kill the demon king but accidentaly helps the demon king in order to stop the demon king from getting accidentaly helped by the system that tries to kill the demon king.