User blog comment:Godisme/Everything But The Rain Op. 2 "The Rudiments"/@comment-1351982-20130306204540

I honestly don't see the hollowfication with happening with Isshin, mainly due to the fact he didn't know the visoreds personally and appeared to not fully understand how the visoreds gained hollow powers. Although it may have been written that way, so that the readers were under the impression that the visoreds were bad guys, I have a feeling that Urahara did not tell Isshin the entire story about the visoreds or Aizen's hollowfication experiments with Shinigami. Also, since this appears to bet after Kaien's death, I would assume that Aizen was leaning more towards research on creating hollows that had high spiritual power and transient beings rather than simply hollowfied souls. When Aizen was preparing to kill Shinji, he said they were excellent research subjects and that he was done with them, which leads me to believe he had ceased research in hollowfication. I see Aizen as one who wants to progress so why would he conduct a past experiment he already "successfully"conducted? Which goes at shows you Aizen's "respect" of Tosen.