Board Thread:General Discussion/@comment-10266932-20130531151056/@comment-11051098-20130901143626

The first version of Zangetsu, as well as the following versions Ichigo got after Urahara's Shattered Shaft-training and the return of his Shinigami powers from Urahara's special sword, was always a special case. All Zanpakutô are based on an Asauchi, but Zangetsu never had that base. It materialized itself from the beginning.

Now, after he learned the truth about his origins and got Zangetsu reforged by Oetsu Nimaiya, it was made from an Asauchi and is now finally a "real" and complete Zanpakutô. Its Shikai has changed into a dual blade Zanpakutô, and because of that, many of us think that his Bankai will change too.