It turns out that Zhao Yu had travelled to Bai Ling City to not only investigate Cui Lizhu's origins, but to also look for clues about the Headless Female Corpses Case and the Gem Theft Case. So, he really did have ulterior motives!
Actually, he even had a third main goal, which was to look for Cui Lizhu's parents' graves. More accurately, he was searching for Cui Lizhu's mother's, Du Manting's, grave!
It turns out the story began from the side quest that Zhao Yu had experienced the day before. At that time, the side quest had pointed him towards a funeral that was held in a cemetery, where he met a gold-digging b*tch!
At first, it didn't seem like anything special, and Zhao Yu had scared off the b*tch, not thinking anymore of it. At least, not until night, when Zhao Yu read through the case information and suddenly had a great discovery. In Cui Lizhu's testimony, there was a crucial piece of information that had been recorded.