A Thought of Mortal Life, a Long Song of Shadows

The story is set in the fictional Tanghua Kingdom, modeled on the prosperous Kaiyuan era under Emperor Xuanzong of Tang. Beneath its outward prosperity, danger lurks everywhere. The capital, Tanghua, is bustling, but that masks problems such as corrupt officials and threats from foreign enemies.

Modern kindergarten teacher Lin Chuyu transmigrates into the body of Ye Qingyin, an illegitimate daughter of a family of shadow guards, and joins their organization. During training and missions, she meets Lu Li, the shadow guards' leader, and Yun Xiuran, a junior minister at the Court of Judicial Review. As the heroine takes on missions, Pei Su's schemes begin to surface. She grows closer to the male lead as they work together, and their feelings deepen.

The heroine is drawn into a struggle for power and begins to question the shadow guards' mission, bringing her into sharper conflict with Lu Li. She and the male lead join forces to investigate and uncover the truth. Pei Su's coup erupts, leaving the heroine facing a difficult choice. The emperor's ruthless exploitation of the shadow guards drives them apart. In the end, the heroine, the male lead, and Lu Li work together to thwart the coup, but Lu Li sacrifices himself. Having grown amid both prosperity and disillusionment, the heroine sets out on a new journey.