Board Thread:General Discussion/@comment-4115054-20140903063305/@comment-24317446-20150403033130

"You have lost, Kurosaki Ichigo. Behold! My Zanpakutou is disappearing. You of all people must understand what this means. The Hōgyoku has determined that I no longer require a Zanpakutou! I will be like you, who became one with his Zanpakutou and his powers! No, I will eclipse you, who have now lost those powers, and conquer heights far beyond your imagination! You're finished, Kurosaki Ichigo!" - Sōsuke Aizen, before Kisuke Urahara's sealing Kidō activates

Aizen clearly states here that he is currently merging with his Zanpakutō spirit and gaining its powers. Though you can argue that the Hōgyoku rejected Aizen as its master, there is still the question of when exactly it did this. After rewatching the scene, it seems to happen once Urahara's Kidō goes into effect, which by this time, it is safe to assume Aizen's Zanpakutō has already merged with him.

Perhaps people do merely have to be in Aizen's presence now for Kyōka Suigetsu to activate, or there is a different method in hypnotizing them now that he has merged with its powers. Aizen couldn't have been able to use Kyōka Suigetsu to get himself out of prison, seeing how he was being sealed. Here's why.

"Try to recall what I said to you. Earlier I explained to you that Extinguir exists solely to seal the flames of Ryuujin Jakka. To seal them means to lock them inside the sword so they cannot ignite." - Sōsuke Aizen hinting to Genryūsai Shigekuni Yamamoto about his sealed flames

Essentially, Aizen states that to seal a Zanpakutō's powers means to lock them inside the blade. Now that Aizen has merged with Kyōka Suigetsu, technically, he is the blade. This means that once Aizen was sealed, or even while he was being sealed, the use of Kyōka Suigetsu's Kanzen Saimin was not possible, effectively ensuring his imprisonment.

I am 100% sure that Aizen has merged with Kyōka Suigetsu. Though Xilinoc states that Kanzen Saimin can't affect time perception, current studies show that time perception is actually a sense of the body. Though I admit that Aizen states that Kanzen Saimin only affects the traditional five senses, there is nothing stated about his Bankai, which Aizen would have quick and easy access to since...he is his Bankai? Though this is only theoretical, it seems much more likely than "Yhwach forgot what time it was".