Tbh I personally prefer it when their mentality regresses, it's what I always headcanon whenever the protagonists acts more like a child or a mix of a child and someone who is older. I get not everyone enjoys that tho.
It could be because I believe the soul to be separate from the body (at least theoretically, when thinking about regression/possession) and is mostly just the thing to breathe life into a body. A lot of other factors are decided by the body itself, such as the brain. Souls can carry memories and personality, but a lot of things are about the physical body.
Again, these are just my own thoughts thanks to being a huge nerd lol. I very often think about trasnmigration/possessiom stories and what they could do with this concept - ie. Body 1 was neurodivergent/had ADHD and/or ASD, but body 2 has neither and is very neurotypical. Brain is structured differently, you see the world differently, even if you have your og personality and memories. Or body 3 was a cis woman, but body 4 is a trans man - this doesn't change anything in their bodies even if their souls are switched, as the brain is where things come from.
(￣∇￣")
based take. so real bro.
why they got beef with a child?? what is even happening?? (i expected the fl to be a bit more.. idk, cunning? she is the villain's daughter after all, i thought she'd utilize her knowledge more but she seems to have also regressed to a childlike mentality