User blog comment:Toshiroichigo/Lack of strong personalities among vice captains./@comment-1771627-20131103053313/@comment-4207271-20131103061239

The fact that he knew (or at least showed no reaction) about how brittle the edge of his Bankai is implies that he had previously broken it, maybe his could share the uniqueness of Kokujo Tengen Myo'o? They do seem quite close.