It was her eyes that caught his attention. When she
spoke of the Kurosaki brat, her eyes were so sad. They practically screamed "notice
me, hear me, see me" and he couldn't help but notice her. He couldn't help but
listen to her and he most definitely saw her.
Even when she cried herself to sleep at night, calling for her beloved to rescue her, he was there. Watching. Listening.
And when the Kurosaki brat showed up, Ulquiorra wanted to pummel him. He wanted to kill him and make her stay but that wasn't what Aizen-sama wanted and he always did what Aizen-sama
So he watched her leave, happily following the boy that would never love her back to their home. Again, he was hit with the urge to beat that brat to a bloody pulp and leave Grimmjow
the remains in a neat, tiny little box with a tag saying 'happy eating' or some other such nonsense.
Instead, he just turned around and didn't look back. He
went back to his duties. There were things he needed to do, things that he couldn't
ignore. Starting with cleaning her room.