C216 Why is the set bitter

Hearing that, Xiao Long pondered for a while, before slowly saying: "Miss Zhen, let me tell you the truth. I have always thought of Yu as my younger sister, and I have no way of making any spark of love with her. Most of the time, I really feel like I'm using her as a substitute for my sister. I know that's not appropriate, or maybe it's unfair to her, but no matter what