
This is my theory
I think they are not human turn animal but animal turn humanoid. Fluffy seems to be that if we see last chapter as foreshadowing on Fluffy. I think what Little A see is animal human transformation and his parents didn't believe in him and thought he is insane or traumatized. So I guess the memory of the past is just make up stuff that animal believe they are

Ooooh that actually makes a lot of sense and I also noticed fluffy as a dog but I didn't pick up that he transformed from dog into human . But it doesn't explain how Mr A had goat (or some sort of animal) ears so maybe there's a mix of humans transforming to animals and animals transforming to humans. That might also explain why some people like M and K didn't go crazy when they remembered their lives because they did actually have a life but other people that transformed into a human did go crazy and try to kill themselves because they were confused or shocked or something
https://comic.pixiv.net/works/11595
Thank you!!