Black magic is involved.

Shen Yu's face turned red in anger but she still bit her lip and didn't make a fuss, even though she was angry she knew that Gu Chenyi did not have any feelings for her. He was only engaged to her because the head of the Gu family wanted a talented woman like her to become his granddaughter-in-law and nothing more, if she was to say anything unsatisfactory then he will definitely rip her face in front of the others. Shen Yu was upset but she could only suppress her anger and then act as if nothing happened, she even smiled at Gu Chenyi and showed the expression of that of a loving fiancée as she hugged his arm and coquettishly said, " I was trying to chase after you in a hurry and in my hurry I slipped on the floor, are you angry with me?" 

She was the woman who won over the old master Gu and she of course knew all the tactics that a woman knew to win over a man, it was such a pity that Gu Chenyi was simply a block of ice who did not care about her at all.