User blog comment:Xilinoc/Ch. 540 - The Sword Five/@comment-7630025-20130606091757/@comment-7630025-20130609103927

Also in the flashback Isshin never used getsuga tenshou so his powers may be effected from the link with a quincy as well, not to mention the original getsuga was taught by zangetsu and if his zanpaktou is actually take over by zangetsu it makes it a quincy weapon instead. the black getsuga is ichigos technique or Kuroi Getsuga. Getsuga Tenshou the original may be a quincy technique of its own