User blog comment:Godisme/My Take on Isshin/@comment-1970867-20100328185743

Isshin is most likely a vizard, because when Ichigo was created he was born with the hollow. Also Isshin is extremely near the vizards... A likely connection.

And finally I think the former captain of the 11th squad may be Isshin. He must have faked his death to have a life in the human world