Based on a popular webtoon of the same name, "Moon in the Day" tells a thrilling and poignant romance story that bridges the Silla Dynasty and the present day. The plot follows Han Jun-oh, a top Korean star who is deeply insecure, and Kang Young-hwa, a former firefighter turned bodyguard whose life changes after saving him. During a commercial shoot gone wrong, Jun-oh's body is possessed by Do-ha, a vengeful and elite noble from the Silla Dynasty who was murdered by his beloved wife, Han Ri-ta. As Do-ha navigates the modern world inside Jun-oh's body, he discovers that Kang Young-hwa is the reincarnation of Han Ri-ta. The series explores the complex and agonizing entanglement between the two, as Do-ha seeks revenge for his tragic past while simultaneously fighting against lingering feelings of love and protection. Secrets of their past lives unravel, revealing a complex web of betrayal, destiny, and unfinished emotional business.