Curate, connect, and discover
Hehe, I am thinking that JC got tangled in some shenanigans that keep following Wei Wuxian, and in effect got sent to some other dimension where everything is the same but isn't.
And now WWX has to go and retrieve him - and for that ends up going through quite a few realities in a "Where isy my shidi?" adventure that places him face to face with a variety of Jiang Chengs and his own feelings of shame, guilt, love and anger towards his shidi.
He sees a Jiang Cheng who have lost their core and a one that didn't, ones that reclaimed his sect and one that was enslaved by Wen Zhuliu as some sick standin for his mom. One that saved Yanli and sacrificed his sect and one that never forgave Wei Wuxian (ohz so that's how his actual hate feels) and one that got over WWX's death and forgot (and that's how indifference feels, Wei Wuxian hates it!). There is a reality where JC didn't get a replacement core and Wei Wuxian was the Jiang Sect Leader who kept him under lock and key (and that Jiang Cheng was miserable, but didn't want to run away, as long as his Wei Wuxian loved him still...).
There is one where Jiang Cheng is married to Lan Xichen and they have kids??? (Wei Wuxian hates it! Hates it! Hates it!!! ....just can't explain why... His shidi would never...right? And what does it mean Jiang Cheng gave birth to the kids?? Oh gods, he never wants to have Lan Xichen sit him down for a sex talk ever again>_<!!! The alpha/omega sex sure is something!) That world unsettled him the most. How is it that Jiang Cheng is happily married here? How is it that Lan Xichen chose him to marry??? Doesn't he mind the awful personality and constant anger? His shidi is very pretty and great, and strong, but he is just like his mom and... Lan Xichen almost slaps him in the head in that universe. Which is scary, because Lan Xichen never gets angry to Wei Wuxian's memory. And on account of a joke? Wei Wuxian doesn't get it.
"If you stopped looking at him and trying to see his mother instead of the boy you grew up with." The big alpha tells him. "Then you'd understand."
And uh, yeah, that one kinda....stung a bit. Maybe that reality wasn't that bad - for Jiang chengttonhave someone who cared for him and understood him. For his shidi to have family again, one that loved him as he should be loved even if it didn't include Wei Wuxian. Even if his shidi had to birth babies and take that monstrous Lan pillar...(he hated it, hated it, heated it!!!)
It's still better, however, than the one reality Wei Wuxian stepped into that just... Didn't have Jiang Cheng of its own. One where he died at the hands of Wen Chao, where the Sunshot Campaign never even got off the ground, because their Wei Wuxian burned the Wen to the ground and salted the ashes. There's no Lan Sizhui there, no Wen Ning. Wen Quing died under his hands like all the others. There's no Yunmeng Jiang. Just Wei Wuxian full of rage and the world that lives in fear of him. What a miserable existence.
He left that world as fast as he could, sick to his stomach.
On the quest to reclaim his precious shidi.
AllAlone!WWX would most definitely breach containment after original WWX and JC leave. Because why would he stay in his own empty/lonely world if he doesn't have to? There must be plenty of JCs out there, surly one is in need of a shixiong? Who knows, maybe he could even gain a whole collection of them too.
An adult JC because he always wanted to see JC grow into his gorgeous self, a teenage JC, one that he himself saved even, to fix his past sins, a child JC because he's simply too cute to leave out, same goes for the catboy version he found, and he especially had to save his shidi, this time shimei, from being married off to Wen Chao of all people. With so many JCs he would never be alone again! . . . Oh god he would start a sort of Shidi war now wouldn't he?
Oh, he'd absolutely get ideas after meeting Another Himself from a different dimension where Jiang Cheng survived. He'd 100% interrogate the Canon!WWX and learn that there are other worlds where JC lived.
And it would stay with him and torture him for days, weeks, months... And he'd tell himself that he won't do it, that he can't, that Jiang Cheng that's happy where he is should be left there, that he couldn't hurt them...
But, if there was Jiang Cheng that wasn't happy where he was? If there was Jiang Cheng that was left without Wei Wuxian? Alone in a ravaged, sect, without his golden core without support, unprotected from the greed of other sects... His shidi that was always trying to hard, that was ready to give from himself until nothing was left for the safety of his loved ones... How could Wei Wuxian leave him to such terrible existence?
And so it starts, the mission of finding a shidi for himself. And the longer it goes, Wei Wuxian isn't even lying to himself anymore - he's doing this for himself. He cannot be in a world where his Jiang Cheng isn't. He cannot live with himself and his guilt anymore. He won't.