Set off by a sweet chance encounter, 16-year-old Su Zaizai finds herself helplessly drawn to Zhang Lurang — her smart, charming yet distant schoolmate.

During the Zhenyuan era, the accidental death of the Bai Ze goddess, who governed both human and demon realms, leads to chaos as demon beasts run rampant. Disguised as Zhao Yuanzhou, the demon leader Zhu Yan offers to form a demon-hunting bureau to help restore order. Wen Xiao, suspicious of Zhao Yuanzhou, joins the bureau along with her childhood friend Zhuo Yichen, skilled archer Pei Sijing, and the talented but timid doctor Bai Jiu. Together, they confront the creatures from "The Classic of Mountains and Seas" and uncover the darker truths behind the chaos.

Under the city of Chang'an, there is a hidden mystery, where secret lovers return at midnight. A proud young lord and a spoiled noblewoman live a double life: by day, they enjoy their romance, and by night, they fight fiercely, all to protect peace and ensure a calm world.