User blog comment:Godisme/Everything But The Rain Op. 2 "The Rudiments"/@comment-4957813-20130306155924

Hmmm it seems to me that the Vizards will come into play. Also, considering the Vizards were hostile to Shinigami at that time, they probably would have had something to do with Isshin's defeat, though I'm not yet sure as to how or what their role was, if any.