I've been reading for some days almost all fanfics of Kenpachi (in AO3 & FF.net) and I've realized there isn't fanfics about the disappearance of Yachiru when he releases his shikai and bankai. I think would be pretty interesting read (or write) about the feelings of Zaraki, no when she disappears but later, when the war ends and the truth hits him. Yachiru is gone. She never will be with him.
I'm sure he would be devastated (my poor man 🥺)