User blog comment:Lia Schiffer/418: Deicide 20/@comment-1439341-20100902200620/@comment-1685879-20100903102533

if isshin taught ichigo the FGT, then isshin must have already used it already. I was just wondering what if, because isshin used the FGT, his reiatsu almost vanished (remember his talk with Uruhara?). anyway, i maybe wrong.. i just thought of this when finding an answer to unjustify having new stronger-than-aizen villains.