Listening
Yachiru Enjoyed telling Byakuya any story she could think of. At least once every week she would settle herself in his office and after greeting him begin weaving her various tales ranging from the random brawls the erupted in her division to the latest hollow she killed with Captain Zaraki. Those in the sixth division who passed by while she was reciting all assumed their stone faced Captain was simply ignoring her like he did with most distractions. Those who walked into the office helped to enforce this idea as no matter how wildly the pink haired lieutenant gestured or paced about Byakuya never looked up from his piles of paper work.
This made people question why she continued to come every week.
The reason was she noticed something they didn't. When she talked his brush moved in time with her words, whenever she paused to breathe so would his hand. When she ended a sentence he'd take the chance to dip his brush before she continued. That's how she knew that even though he wouldn't stop working he was listening to her and that kept her coming back.