Possibility

[Coca]

I think the reason for Aizen's interest in Ichigo is simple:
The whole "Destroy Karakura Town" plot is just a ruse to distract everyone from Aizen's real goal: Ichigo.
Aizen doesn't need thousands of souls to create the Ouken, just one special soul, which would be Ichigo since he's something like highly condensed darkmatter reiatsu. Did you notice how Aizen was feeling Ichigo's dark reiatsu as it slipped through his fingers? That's just him checking to see if Ichigo is ripe for the harvest, aka Ouken time.

How did Aizen learn of Ichigo's existence? Simple:
When Aizen was sifting through the confidential archives in SS regarding the Ouken, he probably spotted something regarding the use of special reiatsu to recreate the Ouken which manifests once every century or so not in an area like Karakura as the shinigami had thought, but in one person, Ichigo.
Notice how throughout the beginning of the series, everyone around Ichigo seemed to gain heightened spiritual awareness or abilities like Inoue and Chad? I recall Ishida mentioning how Ichigo simply "oozes" reiatsu affecting all around him, even amplifying Quincy powers merely by contact. I don't think this "amplifying" characteristic applies to anyone except Ichigo, which is his defining characteristic. Central 46 probably knew that Ichigo's characteristic would show up every few generations and was constantly on the lookout for it due to its Ouken potential, which may be related to Isshin and why he left SS. With Aizen scheming to create the Ouken WAAAAAY before he even became a Captain, he probably caught wind of Central 46's concerns regarding the characteristic "reiatsu anomaly" ie Ichigo, and focused on areas with high spiritual concentration, and then pinpointed Ichigo after his first encounter with Rukia when she used a binding spell on him, which he broke through despite being just a "human".

Basically, all of it, as Aizen said, was leading up to this pivotal point in the series. So yeah, it's "Strawberry" harvesting time.

[AmarSa]

It's very unlikely to me that Urahara and Aizen worked together anytime in the past, it would just turn around some things in Bleach for 180 degrees.
Why would Urahara seal the Hougyoku in Rukia, he could just have hand it over to Aizen.
But it's possible that Isshin has a good history in SS, obviously he was a captain, maybe Aizen kept an eye on him after he went to Karakura town..and after that Kisuke, if Aizen knew that they know each other he could've planned something for his own desire.

When the C46 sent Byakuya and Renji to come to pick up Rukia in the real world, that was in fact Aizens order to get a hold of the Hogyouku, so he certainly knew that Ichigo is in the game, and eventually that he is Isshins sons.
He was not introduced for nothing, so I think that sooner or later Isshin will have a role in the actual plot, at least I hope so.

That's just a theory, let's see with what Kubo will come up.

[kabe87]

There is a vesion in onemanga that aizen says "just as I expected" and not "just as I planned" I dunno but expected makes a lot more sense than planned imo

[Hand Banana]

I think the reason for Aizen's interest in Ichigo is simple:
The whole "Destroy Karakura Town" plot is just a ruse to distract everyone from Aizen's real goal: Ichigo.
Aizen doesn't need thousands of souls to create the Ouken, just one special soul, which would be Ichigo since he's something like highly condensed darkmatter reiatsu. Did you notice how Aizen was feeling Ichigo's dark reiatsu as it slipped through his fingers? That's just him checking to see if Ichigo is ripe for the harvest, aka Ouken time.

How did Aizen learn of Ichigo's existence? Simple:
When Aizen was sifting through the confidential archives in SS regarding the Ouken, he probably spotted something regarding the use of special reiatsu to recreate the Ouken which manifests once every century or so not in an area like Karakura as the shinigami had thought, but in one person, Ichigo.
Notice how throughout the beginning of the series, everyone around Ichigo seemed to gain heightened spiritual awareness or abilities like Inoue and Chad? I recall Ishida mentioning how Ichigo simply "oozes" reiatsu affecting all around him, even amplifying Quincy powers merely by contact. I don't think this "amplifying" characteristic applies to anyone except Ichigo, which is his defining characteristic. Central 46 probably knew that Ichigo's characteristic would show up every few generations and was constantly on the lookout for it due to its Ouken potential, which may be related to Isshin and why he left SS. With Aizen scheming to create the Ouken WAAAAAY before he even became a Captain, he probably caught wind of Central 46's concerns regarding the characteristic "reiatsu anomaly" ie Ichigo, and focused on areas with high spiritual concentration, and then pinpointed Ichigo after his first encounter with Rukia when she used a binding spell on him, which he broke through despite being just a "human".

Basically, all of it, as Aizen said, was leading up to this pivotal point in the series. So yeah, it's "Strawberry" harvesting time.

Very well put.

[Jaiden]

I think the reason for Aizen's interest in Ichigo is simple:
The whole "Destroy Karakura Town" plot is just a ruse to distract everyone from Aizen's real goal: Ichigo.
Aizen doesn't need thousands of souls to create the Ouken, just one special soul, which would be Ichigo since he's something like highly condensed darkmatter reiatsu. Did you notice how Aizen was feeling Ichigo's dark reiatsu as it slipped through his fingers? That's just him checking to see if Ichigo is ripe for the harvest, aka Ouken time.

How did Aizen learn of Ichigo's existence? Simple:
When Aizen was sifting through the confidential archives in SS regarding the Ouken, he probably spotted something regarding the use of special reiatsu to recreate the Ouken which manifests once every century or so not in an area like Karakura as the shinigami had thought, but in one person, Ichigo.
Notice how throughout the beginning of the series, everyone around Ichigo seemed to gain heightened spiritual awareness or abilities like Inoue and Chad? I recall Ishida mentioning how Ichigo simply "oozes" reiatsu affecting all around him, even amplifying Quincy powers merely by contact. I don't think this "amplifying" characteristic applies to anyone except Ichigo, which is his defining characteristic. Central 46 probably knew that Ichigo's characteristic would show up every few generations and was constantly on the lookout for it due to its Ouken potential, which may be related to Isshin and why he left SS. With Aizen scheming to create the Ouken WAAAAAY before he even became a Captain, he probably caught wind of Central 46's concerns regarding the characteristic "reiatsu anomaly" ie Ichigo, and focused on areas with high spiritual concentration, and then pinpointed Ichigo after his first encounter with Rukia when she used a binding spell on him, which he broke through despite being just a "human".

Basically, all of it, as Aizen said, was leading up to this pivotal point in the series. So yeah, it's "Strawberry" harvesting time.

Nice thought man.

[jedijuck]

that is a nice theory coca and would make sense. im thinkin aizen is watchin ichigo for a diff reason. maybe as a way to see how far he enhance his own powers. it may be due to ichigo being human, but it seems he doesnt face the same barriers that shinigami do in trying to become more powerful. who knows cant wait for next week.
i still reference back to http://www.onemanga.com/Bleach/315.12/16/...no matter how far aizen has schemed, i think urahara has matched him. im still waiting to see when he makes an appearance.

[LeaT]

I think Aizen knew of Ichigo before Rukia arrived to Karakura Town. I think it was in fact Aizen who sent her there in the first place. This definitely ties to Isshin though, and I already theorized long time ago that Ichigo was needed to create the key as well. Aizen knowing of Ichigo's existence isn't all that odd, considering that Urahara knew of Isshin already for example, and it was in Aizen's interests to keep an eye on Urahara and what he was doing on the human world. I however believe that what makes Ichigo special isn't so much his reiatsu type, but rather the fact he is half-human, half-shinigami, and now also half-hollow more or less. At least I would assume this is one of the prerequisities of whatever Aizen is scheming for.

[Chaos Shepherd]

Ichigos reiatsu didnt really amplify ishidas quincy powers.. ishida was more or less "taking" the reiatsu that ichigo was sending out.. But i do believe it was stated that he was the one that gave orihime her powers.. Not sure about chad..

I wonder if it was possible for aizen to change the file of what he had looked at... (how to make the key) I wouldnt be surprised if he had changed it, anyway. This way it would ensure that ichigo would come after him because he was going after karakura town. It would play into the "aizen controls everything" theme this manga has..


Aizen could have found out about isshin through urahara, but it wasnt like he was hanging out with urahara that much.. He would have had been constantly watching urahara almost... (if you believe that they didnt meet up a lot..) But they could, there hasnt been much of an indication that they didnt meet up a lot. Kubo has only indicated that they knew of each other.. Although, this is probably the most likely way he found out about isshin, if he did anyway.

[Shinhan]

Ichigo is gonna lose it when he finds out that Aizen sent Grand FIsher to kill his mother...

[Coca]

what makes Ichigo special isn't so much his reiatsu type, but rather the fact he is half-human, half-shinigami, and now also half-hollow more or less.

So Ichigo's basically Man-Bear-Pig: Half man, half bear, half pig.

Ichigo is gonna lose it when he finds out that Aizen sent Grand FIsher to kill his mother...

Naturally this would be the, "Awaken-spiritual-awareness-through-traumatic-incident" part of Aizen's grand, master plan.

Or, OR, Aizen's just bitter because Isshin got the girl, and was all: "If I can't have her, NO ONE will!" However, after having Ichigo's mother killed, he deeply regrets it and now wants to become god so he can go back in time and undo the past and hook up with Ichigo's mother before Isshin does, making Aizen Ichigo's future-past-time father. It ALL MAKES SENSE NOW! Aizen, despite his cold exterior, is just a romantic at heart. *sniff* *tears*