Just to throw this analysis out here because of the "twist" in the plot
CH 396 - The beginning a long series of explanation. I actually think it's not too far-fetched and that it was planned, if not from the very beginning then since the Arrancar arc. There were subtle hints in the manga/anime that relates to Aizen's "planning":
- Back when Ishida was using his hollow bait to have his showdown with Ichigo, he stated that his hollow bait would NOT attract that many hollows, let alone a Menos Grande. This can be explained if someone sent the hollows there. [side note: Urahara said that "this battle is a crucial battle. As crucial to you [Rukia], as it will be for him." So it either meant that Urahara saw Ichigo's potential, or that Urahara foresaw Aizen's plan...and was plotting against somehow] Aizen said that this battle was for the "awakening of his shinigami powers", that is to release Ichigo's true potential. It also needs to be noted that SS took action to arrest RIGHT AFTER this event occured
- This wasn't in the manga as far as I remember, but in the anime Rukia said in one of the episodes that hollows keep attacking Ichigo "as though someone was sending them"
- Ch 75 pg 12-13 When Gin first met Ichigo, he identified Ichigo without being told of his full name - i.e. he had known his existence previously. Since we now know his involvement with Aizen we can assume that Aizen knows Ichigo back then too.
- Ch 79 pg 9-13 Aizen was talking to Renji about possible conspiracy within the Gotei 13. This was never fully explained, but with Ch 396 we can say that Aizen was egging on Renji to fight with Ichigo. Renji, albeit already having a grudge against Ichigo from nearly defeating him in the real world as well as taking away Rukia's power and thus sentencing her death, did not necessarily have to take off his Vice-Captain Badge, seek out Ichigo, and eventually ask Ichigo to save Rukia as he recognized his defeat
- CH 198 pg 10 Aizen sent Ulquiorra and Yammy to observe Ichigo, and the replay only focuses on Ichigo, signifying Aizen's focus on him. Before one would assume that Aizen was assessing Ichigo's potential of becoming a "threat", but we can safely say that there is a deeper meaning to this. 1) Since he left SS, he needs other method to stalk Ichigo 2) Warns Ichigo of what's to come and that he must attain that level.
- Ch 255 pg 5 Aizen comments on Ichigo's fight with Dordonh, "It seems that he had a little more trouble that I was expecting. I had thought that he'd be able to take care of an opponent like Dordonh a bit more quickly..." Meaning, he was keeping tabs on Ichigo's "improvement". He, along with Gin, was "enjoying" Ichigo's group getting closer to the centre of LN.
- Ch 388 When Ichigo was attacking Aizen, Aizen was taking more like a "teacher attitude" towards Ichigo rather than really fighting him. "The attack was good, but the location was poor." As well, "You can't protect anyone with it. Your helpless fans serve as nothing more than weights to hold you back." is right on Ichigo's weak spot. Aizen must have been observing Ichigo for a while to know Ichigo's ultimate resolve was "to protect"
- There was a reason why Aizen didn't cut Ichigo down / show his Shikai the moment Ichigo entered the battle field in fake Karakura town or in HM
Several mysteries still remain unresolved, however:
- If Aizen DID plan it all out, then what of Urahara's involvement? (that is, giving Ichigo shinigami's and hollow's power, guiding him to HM)? Does it mean that he too had been a piece of Aizen's plan, or he's just going with the flow and somehow counters his plans? How DID Aizen predict that Ichigo would gain hollow powers? (unless of course Aizen is well-informed of the only other way for Ichigo to regain his shinigami's power is to become a hybrid) Gut feeling: Urahara's not part of Aizen's team, as shown in TBTP arc
- When and how did Urahara planted the Hogyoku into Rukia (because I think this is somehow related)? Rukia is approximately 150 years old, meaning she existed before the TBTP arc, however, she did not become a shinigami until much, much later. In the End of Hypnosis series, Aizen states thathe knew Rukia had the Hogyoku in her before she left SS. If Aizen truly did plan it so that Rukia would meet Ichigo, he must have knowingly let Rukia left with the Hogyoku in her soul, foreseeing all the consequences (e.g. saving Rukia, Urahara's involvement) that follows.
- Hogyoku's true ability and the reason why Aizen implanted it in himself
- How did Aizen "see" the fight between Ichigo and Ulquiorra? However, going back to Ch 255, he never really needed any "report" to know a) Ichigo was fighting Dordonh b) Someone sent the exequias c) Szyael Apollo's research. So one can assume that he has thorough knowledge of LN
- WHY would Aizen manipulate Ichigo's movements up until now? [let the crazy theories begin] Does this mean that all the events that happened in SS arc's "End of Hypnosis" was a ruse? So the whole SS arc was made so that Ichigo can go and toughen himself up (and getting the Hogyoku in the process)? in Ch 175 Aizen said to Ichigo, "Your mission is over" - refering to Ichigo learning his bankai and "taking a step towards Hollowdom", which Ichigo would not be able to master/learn without the vizards', who are in the human world, help? His betrayal WAS revealed after Ichigo's hollow form took over. It would make sense now why he said so ruthlessly to Rukia, "You no longer are of any use to me," because Rukia already lured out Ichigo, AND gave Aizen the Hogyoku.
- How does Isshin/Ryuken tie into all of this?
Heck, I wouldn't be surprised if the Grand Fisher's attack on Masaki was planned by Aizen too.
P.S. BTW Did anyone notice that Aizen stopped called Ichigo "Ryoka boy" in this chapter? And somehow know Ishida's full name and calling him thus instead of "Quicy" like other Shinigami [or, rather, Mayuri only] (this must mean Aizen knows about Ryuken too?)?