Mei Zhuyu, a calm and reserved nobleman from a lesser branch of the Mei family, arrives in Chang'an as an official at the Bureau of Mystic Investigations. During a banquet, he meets Wu Zhen, the bold and unruly younger sister of the Empress and secret Guardian of the Demon Underworld. Both hide their true identities. Wu, a half-demon striving to keep peace, and Mei, a skilled demon slayer, seek the truth behind the fire 18 years ago. As bone demons rise and unrest grows, they fight side by side, forming a bond that deepens into love until the Changxi Palace launches a purge, forcing them to face each other's secrets and the past they share.

Pessimistic novelist Ji Shu, known for tragic endings, clashes with optimistic screenwriter Song Yan Qi, who wants to adapt his work with a happy ending. When they are pulled into his novel, they must rewrite the story while navigating their growing feelings—unsure if their own tale will end in joy or heartbreak.

A materialist scholar strays into a demon's realm, only to rediscover a century-old soul-bond and a love predestined by fate.