That man is Gu Sheng. But the call Nan Zhi received in the morning must have something to do with Master Bai. I guess there is someone trying to cause another misunderstanding between Mu Sihan and Nan Zhi by harming Master Bai.
Now she is worried about an old guy she is met once
I thought when you love someone there is usually mutual trust what's the problem with airing out what she really feels or think as much as its a s story don't make it too unreal