At her betrothal banquet, Zhang Yanci, the legitimate daughter of the Duke of Zhenguo, faces an unexpected change in her marriage arrangement and finds herself caught in a dilemma. Xiao Heng, the regent prince known as the Buddhist Son and afflicted with an old illness, steps forward and, by imperial decree, marries her. In this contractual marriage that begins with an act of assistance, she uses her medical skills to nurse his health, while he uses his power to protect her dignity and integrity. Standing side by side, they untangle disputes and worldly conflicts, and through their daily companionship, they discover a sincere love that both willingly pursue.