He always watches her from afar. Most of the time, she didn't realize it. He always wants to hold her and treat her like how a brother treats his sister. But, his own pride becomes an obstacle for him.
There is a reason why he hates Kurosaki Ichigo so much. The truth is, He envy Kurosaki Ichigo. He envies how Ichigo can be so close to Rukia in just a few months. However, he owes him so much. If Ichigo didn't come to save Rukia, She would've gone now. If Ichigo didn't fight and beat him, He won't rescue his sister from Ichimaru Gin's sword.
No one knows that almost every night, he will go to her room to watch her sleep. He always watches her while she is training. At his free time, he search for her, and watch anything she do. He always watches her from afar.
Somehow, she is always afraid when she faces him. She don't know why, she just afraid to look at him, even after many years living together. She always hope, that one day his attitude toward her would change, that one day she would have a normal brother-sister relationship with him, that one day she could have a nice and comforting chat with him.
If her brother envies Kurosaki Ichigo, then she envies Kurosaki Yuzu and Karin. She envies how they can be so close to their brother. She envies them, because they have a brother that love and care about them. She envies them, because they have such a lively family. She wants to have that kind of relationship with her brother.
Sometimes, she asks herself, why did he adopt her to this family? Why did he adopt her, and then treat her like she doesn't exist? She wants to ask him why. But she can't, because she is too afraid