User blog comment:Godisme/Swords of Origin/@comment-29259794-20130116182847/@comment-2192072-20130117222111

I think this is Kubo's way of trying to big up Kenpachi in the end. It would be a litle cliche to make him all powerful beyond what he is. I think this is Yachiru's (Unohana's) method of teaching the "art of killing." Zaraki always said she was the only person he respected. And his ability to fight is usually tempered by a desire to continue the battle and not really kill, but fight. Unohana seems the cold blooded type. Maybe she'll cause him to actually get close enough to want to kill the only woman he ever cared for, i.e The Art of Killing.