So i just realised something recently
In chapter 55.5 Vanitas tells Misha that he became Luna's kin in order to kill her with the book as she had become a curse bearer.
He claims that's the "truth" of what happened on "that day"
BUT
Curse bearers don't turn into dust when they die. We see this in the chapter where Louis died.
AND GUESS WHAT
GUESS FUCKING WHAT
Luna turned into dust when they died. Which would be theoretically impossible unless Luna was different from other vampires(which they were but..like... we don't know in exactly WHAT way)
What I'm trying to get at here is:
Vanitas didn't become Luna's kin to kill them. He became Luna's kin so that he could use the book to HEAL them but something obviously went wrong in the process and Luna died.