I should talk about plural J more often because I really enjoy the idea that J has truamagenic plurality while Uzis is (umbrella term) endogenic as she acquired Doll and Cyn through core eating but J developed split parts of her so she could hide the parts people found undesirable or parts of her that would get her in trouble from both Cyn and the Elliots.
It definitely would have started at the manor after being revived and thrown directly into an abusive situation with her masters and having to hide her autonomy and individuality. I like to think she'd just assume everyone hears voices in their head because Tessa would ask her if she ever has a voice in her head that tells her shes worthless and J misinterpreted that as literal and agrees.
She'd for the most part talk to the voices and assume it was normal until they started to form their own personality and realized that was Bad and She Can't Have That so she starts ignoring them despite the effort they put into making her better and helping her. She'd eventually bury them so much she'd forget but they wouldn't and get aggresive as they resurface after Cyn was defeated and would get angry seeing Uzi struggle with her own unwanted plurality while they are locked away driving J mad over time.
I also like to think one of them would look like Cyn and torment her soully on that, abuser introject are common in traumagenic based plurality so it makes sense that if she felt uncertain and uncomfortable in freedom she'd develop someone she fears just to remain comfortable in misery despite said "Cyn" not wanting to torture her.
I made names for all of them too the original main host would be J and she'd be so annoying to the others with her claiming to be the only one and their main source of suppression because of her freeze-fawn response to remove all bad things from herself to seem appealing.
The "Cyn" looking one would steal a name from a drone she saw and liked the name and it would be Mckayla and J would refuse to call her or the others any name they have but especially her. She'd insist she cares and wants to help her but her inherent appearance and source would bleed through and cause violent outbursts that would make everyone uncomfortable and Mckayla shameful since she tries not to act like that. She would look like Cynessa with very specific differences like her eyes being white and circular and not yellow Xs and have a more lighter color pallet but still rotten slightly around the eyes primarily.
Then there is the other two who are a package deal but HATE each other, L and T. Their full names are Lily and Titan and they act similarly to Imaginary Friend and Imaginary Pal from Pressure (highly recommend checking out their interactions). Titan is much angrier however and is often aggresive to V, N and Uzi and is easy to tell its him since he deepens his voice and talks more monotone compared to the rest of them. Lily pitches her voice up slightly with a softer tone but is a huge fawn response and is often plagued with acute psychosis from Cyns years of torment. She's the nicest to V but in a way that makes her uncomfortable because of the fawn response. Her psychosis symptoms will bleed into others and cause panic and fear mongering from her and is often the source of Js isolation and rather strange amount of locks on her doors and stock up on specific items for "the end of time itself".
Break down:
J - Host, suppressor (can also count as a persecutor), trauma holder
Mckayla - Abuser introject, protector (unfortunate for her), eventual co host
Lily - Pychosis holder
Titan - Anger holder, Persecutor (due to his outward aggression to N and V)