The furrowed brow and sigh of Qin Sisi made her seem a touch more appealing to Hei Shan.
Hei Shan was harassing Xie Kexin, firstly to draw out the mage that had abducted Yuan Lishu, and secondly to sate his carnal desires.
Beforehand, he had wandered to this area and had coincidentally encountered Yuan Lishu. Yuan Lishu was young and beautiful, very much to Hei Shan's liking.
Thus, the two ghosts, one driven by profit, the other by desire, were drawn together.
After Yuan Lishu was taken, Hei Shan, for some reason, set his sights on Xie Kexin, visiting her every night.
Xie Kexin was entranced by Hei Shan's hypnotic spell, and woke the following mornings feeling weak and fatigued, with no memory of the night's happenings. Her condition worsened with time.
Eventually, she became shrouded in Yin energy and fell into unconsciousness.