AU Concept where the Winter War was a thousand times worse.
At the end of it all, Ichigo rips the Hogyoku out of Aizen's chest and uses the power to send himself back in time. As soon as he arrives in the past (the past, back when Kisuke was still a captain and the Visored weren't Visored and none of all that tragedy had happened yet), Ichigo kills Aizen. He doesn't beat around the bush, doesn't wait for the perfect moment, doesn't try to be sneaky.
After all, why would he? Ichigo is powerful enough to attack straight-out, the tragedy he is trying to prevent is so immense that it truly feels too risky to wait, and he's broken enough that he doesn't care what will happen to him -- an apparent Ryoka -- after killing a Gotei 13 vice-captain for seemingly no reason.
What happens to him is this:
Ichigo is found, kneeling beside Aizen's cooling corpse. Ichigo has Aizen's blood spattered up to his elbows -- it wasn't a clean kill, nor a quick one.
Ichigo lets himself be taken into Gotei 13 custody. (Again, he no longer cares what happens to himself.) He is spared execution for two reasons. First, they need to know who he is and how he did it. It is a scary thing, for a Ryoka to be powerful enough to murder a vice-captain. Second, the Shiba Clan has used their influence to petition for clemency, at least for a time. It is obvious that Ichigo must be a Shiba, and Kaien is desperate to find out where Ichigo came from, who his parents are, and how one of his own family managed to fall through the cracks like this. (Kaien sees it a bit as a personal failure -- what happened, that someone who is clearly his cousin went unclaimed for so long, and became so lost as to murder a vice-captain?)
Cue a series of interrogations (there's no actual torture, it's just verbal questioning, thanks again to that Shiba protection) where Captain Urahara tries to figure out who, exactly, this powerful Ryoka is.
Ichigo -- who is broken in so many ways -- sees how much happier this younger version of Kisuke is, and decides not to reveal anything. Ichigo isn't exactly thinking straight at this point, and he sees no future for himself. So, naturally, he decides that it's best not to spread the suffering around, that it's best to keep the horrors and burdens to himself, and so he keeps his mouth shut about all the important things.
Meanwhile, in the background, Aizen's web of illusions are starting to unravel. Slowly, members of the Gotei 13 wake up. Shinigami begin to realize how far the morals of their institutions have fallen. People realize how much weaker the Court Guard has gotten over the years.
And then people start remembering specific moments where Aizen ensnared them, or made them forget something, or influenced them to take an action they never, not in a million years, would have voluntarily done.
They realize that the Ryoka murderer saved them from an incredible catastrophe.
Ichigo's sentence is mostly lifted, but thanks to Central 46 influence, he's still in a parole-type situation. (Kaien could only do so much. Even with proof that Ichigo had saved them, the Central 46 is still uneasy that Ichigo was able to kill Aizen.)
Ichigo's interrogations continue. It's just that instead of questioning Ichigo in a cold cell in order to find answers in order to protect the Court Guard, Urahara starts subtly prying for answers over, for example, a cup of tea in the Shiba family gardens -- so that he can better understand Ichigo's situation and more effectively help the idiot. Because it's clear Ichigo has saved them all, but it's also clear that Ichigo only knew they needed saving because Aizen had, at some point, broken him.
When enough of Aizen's illusions have unraveled, Operation Help-Ichigo becomes a group effort among the Captains and the Shiba family. (Of course, Kisuke was the first person on the operation, and he's not giving up his lead role, not even now, when everyone else has finally gotten on the same page.)
Cue the bonding with Ichigo. Kaien, Shinji, Kyoraku, everyone, they're all trying to help him.
Ichigo, of course, thinks this is all part of the interrogation routine. He thinks they're trying to manipulate him into opening up, and then once he talks, they'll throw him into a cell to rot for the rest of eternity. It takes a while for people to notice this miscommunication, and even longer for Ichigo to believe them when they try to rectify it.
Thanks that happen at some point:
Someone realizes that Ichigo is actually really, really young. This revelation has all the expected consequences.
Kaien holds it together in the moment, when he realizes that Ichigo thinks his attempts to bring him into the family are just a prolonged interrogation method. But once he's alone with Miyako, he cries his heart out.
Kisuke uses a specific onmitsukido technique to trick information out of Ichigo, but Ichigo knows Kisuke too well to fall for it. Even if Ichigo can't tell exactly what Kisuke is doing, he can recognize Kisuke's "I'm up to something" body-language.
Shinji and the other Visord start noticing a strange connection with Ichigo. (Pack is permanent. Turns out, that holds true both forwards and backwards temporally...)
Ichigo, in his state of emotional numbness, frequently says or does things that betray a high-level of familiarity with people he has no reason to be extremely familiar with. It's through this sort of slip-up that the time travel is eventually discovered.
