During the battle: Aizen vs. The Gotei 13 & The Visored (Episode 292, 293 and 294), Aizen was stabbed by Shinji, Suì-Fēng, Shunsui and Hitsugaya. However, it turned out that Hinamori was stabbed due to Aizen's ability.
To my understanding, Aizen's ability could affect any of the Shinigami in Soul Society because they all had seen his power before. But Ichigo had not seen it and that was why he was considered to be such an asset. Aizen implied that he had been using his ability since he arrived. I would have thought Ichigo would have seen through the ability from the start.
If Aizen had activated his ability before he arrived, Ichigo should have seen through it. If he activated after Ichigo arrived, how did Gotei 13 not see though it earlier?
My questions: when did Aizen activate his ability and switch with Hinamori and how come it affected Ichigo?