Si Ren was intentionally guiding Yao Yu, making her focus her attention on the Zhang family father and son, steering things back onto their original track.
Instead of revealing the whole truth, Si Ren left Yao Yu with a mystery, letting her piece it together step by step. As for why he did this, perhaps only he knew.
When the two of them were parting ways, Si Ren called out to Yao Yu as she was about to leave.
Chapter 921