She had actually suspected that there was more to Chen Xi's relationship with Gu Sitian before, because at least someone of Chen Xi's stature should not be so impolite to Gu Sitian.
Plus, she had heard him loudly call out Gu Sitian's name before, even telling her to stop causing a fuss.
Stop causing a fuss, stop it now!
These words felt familiar, as if Lu Zhanbei had said them to her before. She couldn't express the intimate feeling they conveyed, but she felt that only someone familiar would say things like that, therefore...
"Did you just call her... Si Tian?"
It was only after her question that Chen Xi realized that he had unconsciously called her Si Tian. So he casually explained, "Oh! My father and Uncle Gu Baichuan are friends. I've known Si Tian since we were kids..."
"So, you two are friends?"
"Um, yes..."