I am kinda curious to see what would happen if attlantis and yuume ended up in the hands of good holders! What would happen?
A really interesting idea, especially since Yuume's view of humanity actually wouldn't change, because Yuume has never really had an "evil" holder, per se. His dislike of humanity actually heavily stems from the Dreams he saw, hatred for the control humans had over kwamis, and viewing himself as superior to all other beings. If both he and Attlantis had good holders Yuume would still want a world for kwamis without humans. The only major change for Yuume's story would be his desires would only stay as Dreams, with no drive for action to act of them.
Attlantis would be the one whose story really changed. If he had only good holders he would have a lot more hope in humanity, and still enjoy having holders. The city of Atlantis would still be standing, other kwamis would't be angry with him, and he'd never be isolated, which means his path to becoming close with Yuume would have never happened.
The think the kwami that Yuume would end up being drawn too in this AU is Graay, with both disliking humans. Graay would probably be less receptive to Yuume than Attlantis was, but when Yuume mentions his dreams of a reality where humans don't rule over kwamis, Graay just might stop and listen. And with Graay's ability to inflict Order on the human mind and Yuume to bring nightmares to life, they would be able to do a lot of psychological harm.