the correct term is integrated and maybe they will be in the future. who knows?
That's not really how split personality works. Usually the host stays after all the other personalities are gone but occasionally it can be a personality that's not the host that's left. Both Rei and Kazuha could also share but it would be difficult to take away only certain personalities and leave others. You can't just choose those things
take nin from dissociadid. she's the new host of the system, formed after chloe (the former host) and nina (the sexual protector) integrated. she was both chloe and nina but she is also neither of them. nin is her own person.
so it’s called integrated thankyouuuu
can’t they just mix up? I don’t want Rei or Kazuha to disappear.