Orihime had a lot of time to think while she was in Las Noches. There wasn't much more she could do, besides stare at the reversed crescent moon hanging high in the sky outside her window. On occasion, she would try engaging her stone-faced guard in some, or any, type of conversation.
That usually ended in failure.
Almost immediately she'd likened Ulquiorra to the crescent moon, though perhaps for the wrong reason. At first she thought there was more dark, more evil, in him than there was good. While he had complimented her, he'd somehow managed to insult her in the same breath. Not to mention he was the one who had injured two innocent Shinigami, dragged her to Hueco Mundo, rubbed in her face the fact her friends were supposedly dead, hurt Ichigo--the list went on.
Only when she was back in the world of the living, staring at her own crescent moon, did she realize how wrong she had been.
The darkness she'd seen in him wasn't true darkness. His facade of cold indifference hid something more. She didn't know what that something was; she could tell some of it wasn't pure, as she had originally thought, but not all of it. She had seen some light, some good, in him during his final battle with Ichigo. At the time, she'd been too worried about her friends to notice, but he had helped them, in his own way, more times than he should have if he truly was their enemy. Orihime found herself wanting to know more, to know why.
She wanted to know the crescent moon.
But now it was too late. The moon had changed, faded into a new moon, invisible to the naked eye.
And how she wept because of it.