[Pairing undecided, possibly none later + coming-of-age + third-person narration + secret identity + lots of original worldbuilding]
After Xiaolan died, she was bound to a "man" claiming to be a System. The System was completely unreliable. It tossed her a System panel and then vanished without a trace, leaving Liu Xiaolan to fend for herself in a new world. Her new identity was Japanese, and her life was pretty good overall. Setting aside the inexplicable engagement, she'd made lots of friends. But gradually, she realized something was wrong with this world. Cursed spirits? Cursed techniques? Domain Expansion? These things she'd never heard of made Liu Xiaolan feel the danger. What could she do about it? Work hard to get stronger and keep a low profile, of course. She still had a mission to complete.
When she was a second-year at Jujutsu High, she went on a mission with her two "good" classmates. Unexpectedly, she also ran into her cousin. Maybe luck and misfortune really were two sides of the same coin. She was injured during the mission, then died.
Just before she died, she managed to summon the System. Otherwise, she would've been done for. The System promised that if she completed the mission a thousand years ago, she could be resurrected. Liu Xiaolan agreed without hesitation. She still had things to do, and she couldn't just die like this.
Little Scene
Satoru Gojo: "Lan-chan, let me hear you call me teacher." (reaches out with a wicked hand)
Liu Xiaolan: ...
Suguru Geto: "Lan-chan, we saved you, after all. We'd be sad if you didn't call us teacher." (smiling)
Liu Xiaolan: ... (So there really is a reason Senior Utahime calls you scumbags.)
Theme: May every shy girl find a good friend of her own
