User blog comment:Xilinoc/Ch. 684 - The Blade/@comment-24769684-20160728121813/@comment-26091912-20160729030228

Ok, I think I can explain this whole "how did Yhwach get fooled by Aizen's illusions, lol Kubo is trolling again" snafu. It's going to be a pretty long explaination, so bear with me.

Remember way back in Soul Society arc when Aizen pwned Komamura with just Kurohitsugi? Well he didn't actually use his Kyoka Suigetsu when he tricked Komamur. It was the influence of his Reiatsu, hence "even if you're aware of its ability, you cannot escape its influence." The Reiatsu of the Zanpakuto is similar to the wielder, so even Aizen's Reiatsu can deceive opponents (slightly). Similar to when before Hitsugaya joined the Gotei 13, his icy Reiatsu was affecting his grandmother, which is why Hyorinmaru is an ice-type Zanpakuto.

Now, when Yhwach first went to meet Aizen, he was clearly put under Kyoka Suigetsu's spell, proven when he lost track of time during his first fight with Ichigo. Which means that Aizen had already shown him the hypnosis ritual. Remember, Aizen said all that he needs to do in order to hypnotize people is show Kyoka Suigetsu's release just once. So how did Aizen release Kyoka Suigetsu if his blade was completely destroyed in his fight with Ichigo. Well, it was hypothesized by Urahara that Aizen had become way more powerful while in Muken, and according to Aizen, he became one with his powers. So all he needs to activate Kyoka Suigetsu is anyone to step in the presence of his Reiatsu.

Now how does this all explain how he fooled Yhwach, I hear you ask? Well according to this recent chapter, Aizen activated Kyoka Suigetsu as soon as Yhwach arrived (i.e., before he used The Almighty.) But how did Aizen fool him? Yhwach can see why kids love the taste of Cinnamon Toast Crunch, right? Well just a reminder of how powerful Kyoka Suigetsu actually is, Aizen said that it can control all 5 senses, which means he can make a fly appear as a dragon, or a field of flowers out of a swamp. Not to mention its spell can affect victims even after a century. And that's just his Shikai!

Now the theory: what if Aizen actually used his Bankai against Yhwach? Seems strange to ask, seeing as we'll probably never know. But there's reason to suspect this is plausible. Remember when Ichigo and Renji showed up. Aizen had never seen Ichigo's nor Renji's new Bankai before, so how could he have used them in the illusions against Yhwach? Because they were figments of Yhwach's own imagination. Aizen's Bankai doesn't let him create and control illusions, it makes his opponents become fooled by their own imagination. So ultimately it was Yhwach's own heart that was deceiving him, which led to his demise. That and hubris.

Sorry if this was long-winded and not succinct. I have the tendency to ramble when I'm on to something.

@Faelkun, I only called you that because you wouldn't stop whining about how Aizen trolled Yhwach. Now I've given you something to think on.