He didn't really realize anything until he truly understood his desperate desire to save her.
It's true that Ichigo Kurosaki is hopelessly ignorant sometimes, and this was definitely one of those dreadful aforementioned times. Sometimes ignorance is bliss, as they say, and it might have been a blissful time to be ignorant. After all, it's troublesome to realize just as you're running from the huge thing behind you - the Sweeper? Is that what Yoruichi had called it? Ichigo didn't care particularly at that moment for what the thing was called, since he was so hard headed and always rushed into things anyway, whether he knew what he was getting into beforehand or not. But running from this thing was definitely one hell of a time to realize that he was in love with her.
He cringed even thinking the four-letter word. The word that tied men down for the rest of their lives, subject to the whims of the woman who held his heart.
The woman who held Ichigo's heart, however…?
Well, technically she was already dead. But she would be dead, dead - as in, he could never tell her how he felt, never hold her in his arms, never do anything - if he didn't get to her in time to rescue her.
Yes. The her in question is Rukia Kuchiki.
They were going to execute her because of him! It wasn't a thought Ichigo liked to have crossing his mind, but in fact, aside from the realization that he loved her, that was the only thought on his mind. It hadn't even really been her fault that he'd become practically a full-fledged Soul Reaper - she'd only meant to give him a fraction of her powers! Enough for him to save his family that one time! It was he who had taken the rest of her powers, draining her to near uselessness as she slowly regained her powers.
Even as they fell into what Ichigo knew as the Soul Society, rage burned through his veins.
He wouldn't let her die.
He couldn't.
Even as he was lectured later by the woman he came to know as Kukaku Shiba about controlling his spiritual pressure, his mind was focused on Rukia. He had more drive than ever, a deeper meaning and reason to save her before they could kill her for doing nothing wrong. And it wasn't just because it was false justice, nor just because it was his fault in the first place. It was the emotion he never thought he'd be able to feel - not for anyone but his family.
Yet another reason why Ichigo Kurosaki is ignorant.
But one day, in the future, he would be pleased to know that this ignorance is one of the things she loved about him in return.