Du Qiyue's thoughts are quite simple. She just wants Chi Ruiqiu to take the initiative to keep a distance from Pei Shuangshuang. They can be polite but not close, and certainly not intimate.
However, Du Qiyue couldn't say this herself, as saying it would put her at a disadvantage. She hopes that Chi Ruiqiu can spontaneously do this on his own.
But Chi Ruiqiu's intentions are different from Du Qiyue's. He simply cannot understand this little thought of hers, and besides, he feels there's nothing ambiguous between him and Pei Shuangshuang, so naturally, he doesn't think there's any need to keep a distance.
After all, Pei Shuangshuang saved his big brother's life. She saved someone dear to him, so how can he just keep a cold and distant relationship with his savior? What an absurdity.
