Talk:Senjū Kōten Taihō

I think there is a case of Nijū Eishō (二重詠唱, "Twofold Incantation") in this, when Urahara is casting the spell Aizen is pretty unconcerned about it, however after a point in the incantation, Aizen shows surprise and expresses desire to stop Urahara.

My guess is that somewhere in the spell Urahara switches to the incantation of the seal to imprison Aizen, implants the seal inside the Kido and fires it away.