Silence
Between them, there was always silence. Ulquiorra preferred silence to anything Grimmjow could or would say. Ulquiorra preferred silence to any of the choices, the arguments, the things that had to be said. He knew that Grimmjow could never tell unless Ulquiorra said something. But he preferred silence.
Even when Grimmjow pleaded with him to say something (of course silently, or else he wouldn't be listened to), he didn't. Because so much could change with a word. At least in silence, there were no doubts. Even if Grimmjow hated it, the silence, the lack of anything, Ulquiorra figured they needed it.
In silence, they couldn't get to close. They retained a sense of anonymity. They didn't know each other, they didn't speak, they didn't say the words that needed to be said. He preferred silence, and the safety that silence gave him.
Even if Grimmjow hated it.
Owari