In the fourth episode of Three Thousand Crows Kill, Zuo Zichen already knew that Qin Chuan was the princess. Before this, Qin Chuan had always been regarded as an ordinary general, while Zuo Zichen only began to suspect her identity after she was rescued. In the fourth episode, when Zuo Zichen and Qin Chuan were eating together, Zuo Zichen began to suspect her identity through Qin Chuan's eyes and words. Later, he gradually confirmed Qin Chuan's true identity.