User blog comment:Lia Schiffer/397: Edge of The Silence/@comment-1393830-20100328071541

Then the surprise may be what we have speculated in my blog. Aizen has the hogyoku from the exiled Urahara. What if Isshin stole something from SS to keep it away from everyone and implanted it in Ichigo. It sounds a bit wild but if you remember, when Ichigo became a shinigami again after losing his powers, his chain was fully encroached and his mask fully formed and yet he somehow managed to break his mask and become a vizard. My guess is that there is something special about him that Isshin did to him. Something that allows you to gain the powers of a hollow without losing the powers of a shinigami thus creating natural vizards as opposed to the artificial ones Aizen created. Again it is pure speculation but I find it fascinating and the logic makes sense to me