Decapitation and regeneration
I just finished the manga after being a big fan of the anime, and I thoroughly enjoyed it!! It has left me with one question tho-
Kaimans head was decapitated and preserved in formaldehyde, and this later gave nikaido the opportunity to go back in time to fetch him and regenerate him. Could the same thing have happened to Aikawa and even possibly Kai if their heads got decapitated and preserved in an earlier part of the story? Or would this have not been able to happen cause of Holes stronger grip on their bodies?