Uh... how should I put this.
"Mo Xiao" had experienced the destruction of the Main God Space, only to wake up and discover that he had become "Kurumi Tokisaki"!
Some experiences had made him loathe the Main God Space, so he wanted to escape.
After going through School Days of the Apocalypse and Dark Summoner of the Apocalypse, "Mo Xiao" became increasingly convinced that the Main God was seriously injured and that this was a good chance to flee.
But he had never found a way to escape.
Then the missions continued, and he arrived in the Marvel Universe.
While fighting the Destroyer, "Mo Xiao" suddenly awakened memories from his previous life. He saw how he had become a Reincarnator and how he had drunk that bottle of counterfeit "The Evil of This World."
When he woke up, everything was normal. After all, they were old memories, and Mo Xiao's own memories were gradually fading. He merely assumed it was the Main God's doing. (In the original text, Marvel arc, Chapters 141 and 142.)
He feared becoming the Main God's puppet and wanted even more desperately to escape the Main God Space.
At the end of the Marvel Universe arc, he met Odin, the god king.
In the end, Odin "screwed him over," and he gained divinity.
He continued accepting the Main God's missions.
He arrived in the Fate/Zero world.
The instability caused by crossing planes triggered his divinity, and for some reason, he became a Divine Agent.
Not long afterward, he discovered a loophole in the Main God and suspected that other Reincarnators still existed. (In the original text, Fate/Zero arc, Chapter 5.)
He became even more afraid. Egged on by the Red Queen, "Mo Xiao" jumped into the Root in one decisive gamble, determined to succeed or die