Xu Yuan has liked Qin Zheng for a long time, before he killed anyone. He is a murderer, but Qin Zheng is a policeman. Xu Yuan knew that he would be discovered sooner or later, even if he hid it well. He would lock him away until he was discovered... Since he was in the abyss, he would drag him in with him.
Purpose: No matter how powerful you are, you must protect yourself