Board Thread:General Discussion/@comment-35659646-20180522182736/@comment-957629-20190314115218

He stole an Asauchi and Kenpachi imprinted himself and his soul upon it like any other Asauchi that becomes a Zanpakuto able to wield Shikai and then Bankai. If you look at the panel where Kenpachi is shown taking that Asauchi it looks very different from the sword it became later down the line before he ever learned the name of his own Zanpakuto spirit inside. Also, Bleach Wiki:Discussion Policy