Ichigo was a wellspring of power.
The thought often struck him when he watched the girl train in his hidden, underground facility. But the day that she beat finally did what he hadn't been able too and beat Aizen, it really struck him hard. It must have struck Aizen pretty hard too. The differences in their power was too immense for the man to truly grasp.
But even he had been surprised by just how much power she wielded.
For god's sake, Aizen had been using the Hogyoku to become a god!
And Ichigo- extraordinary, wonderful, mindboggling, Ichigo- had quite literally come out of nowhere as a semi-normal human child. And had practically wrapped the Hogyoku in her own incredibly immense power and had overshadowed it to such a degree that even he had thought that his invention had shorted out!
The fact that Ichigo had finally shown that she was more powerful than Aizen in his god form wasn't totally lost on him either.
Imagine, a human that could literally defeat gods. It was such an amazing sight to behold. So much so that for once he was absolutely speechless. His analytical mind turning everything that he knew of the girl over and over and over again until he came to one startling conclusion.
Ichigo was an unfathomable wellspring of power. And as such, she had to be protected at all costs. After all, even he knew the damage that she could do if the wrong people managed to sink their claws into her- was beyond cataclysmic.
So once everything was over and done, Aizen was captured and sent on him way- drooling like a vegetable- possibly from having his brain scrambled by the information overload. And everyone was present and accounted for, he pulled each of them aside and told them that Ichigo couldn't keep doing Soul Reaper work anymore.
His one and only thought at the moment was to hide that immense power of hers from the Soul Society and the greedy bastards that longed to have such power at their fingertips. Even he knew that should they learn of Ichigo's present abilities, that they would hunt her.
Lock her away. Experiment and even dissect her to learn what they could of her abilities. Just how strong they were, how to recreate others with such abilities exct...
He couldn't allow that to happen. Ever.
He had to plan things literally in the span of seconds. And sadly, he wasn't sure if she would listen to him if he told her that it was no longer safe for her to return home to her family. With her power spilling out like it was, she'd accidentally draw the attention of every hollow, still living espada, Meno's, and many, many more.
Her family could get hurt or even killed. And while he knew that she could more or less take care of herself, it was still a risk.
Naturally, Rukia, Chad, and Renji seemed to understand the most just what the situation had snowballed into. And they had agreed wholeheartedly that Ichigo needed to be kept safe.
So once he'd settled on a plan, and went to collect the girl- he was more than a tad bit surprised to find that the kids were going to come with him. He'd tried to reason with them and tell them to stay, but dammit that lot was fucking stubborn. Especially when it came to Ichigo.
They told him in no uncertain terms that she was theirs just as much as they were hers. Which was a little bit of a weird way to over simplify things. But it was understandable at least.
Ichigo tended to inspire loyalty and a strong sense of camaraderie in even the worst of individuals. After all, that was how she managed to gain Kenpachi, and Ikkaku as her friends/rivals.
Looking from one face to another, he was struck by the strength of the kids bond to Ichigo. And upon finally nodding his head in acceptance of the fact that they would be coming with him, they quickly moved to leave and go say their goodbyes.
After all, they would be leaving Karakura Town...perhaps for good.