Moon in the Day

Jun Oh is the top star who is loved as the Nation's Boyfriend. To cover up his scandal, he shoots a public advertisement with the firefighters. At the set, he meets Firefighter Young Hwa, who is committed to her job. An accident occurs during the break, and a mysterious being that has been following Young Hwa goes into Jun Oh. And this being has only one goal: killing Young Hwa.

As soon as Jun Oh gets up, he goes to Young Hwa and tries to kill her. However, he fails to do so because of a mysterious shield that protects her. To get past the protection and seek the chance to kill her, he decides to get close to her. Young Hwa finds Jun Oh odd, but she tries to understand him, thinking he's suffering trauma from the accident. 

Jun Oh and Young Hwa are kidnapped by a bunch of thugs. Jun Oh beats them up while Young Hwa is unconscious. Young Hwa doesn't remember what happened, but she gets suspended for being involved in a violent incident. Jun Oh asks Min Oh to make Young Hwa his bodyguard so that they can stay close. Meanwhile, Young Hwa gets hit by a car and starts dreaming again. 

Young Hwa is hospitalized and has a dream about her previous life. Do Ha lets Han Ri Ta stay at his place as a maid. Ri Ta realizes that Do Ha has been feeling guilty about the lives he took during the war. Finally, Young Hwa wakes up, and it seems like she remembers her dream this time. Jun Oh gets confused and becomes hesitant about killing Young Hwa.

Min Oh asks Young Hwa to stay by Jun Oh's side around the clock for safety. So Ri Bu and his aides suspect Han Ri Ta's true motives, as they find out her identity. Young Hwa is further assured of seeing Jun Oh in her dreams and tries to make sense of his familiarity. Meanwhile, Monk Hae In goes to Jun Oh's company to meet Young Hwa. 

Because of the talisman, Do Ha gets separated from Jun Oh's body and reveals himself to Young Hwa. From Young Hwa's reaction, Jun Oh notices that she sees their past in her dreams. Young Hwa doesn't know what she's going through, and she goes to see the monk who put the talisman on Jun Oh. Meanwhile, Jun Oh tells Young Hwa about their previous life.

Young Hwa is startled as Jun Oh is well-informed about her past and takes him for a stalker. Jun Oh tells her that her dreams are not mere hallucinations, and they are telling their story from 1,500 years ago. Meanwhile, Chul Hwan comes to the company to meet Min Oh.

Young Hwa decides to help Jun Oh by telling him about the dreams she has. However, it's not easy to have a dream every day. Tae Ju's dead body is found near a river, and his will is sent to the police station. Meanwhile, Chul Hwan tells Min Oh about Jun Oh's condition. Min Oh doesn't believe him at first, but Chul Hwan tells him there is a way to save Jun Oh.

Chul Hwan tells Min Oh that the evil spirit was created because of Young Hwa when she committed a sin in her previous life. Min Oh asks Young Hwa to take Jun Oh on a breakup trip, so that he could use the chance to get his brother back. Meanwhile, Na Yeon finds out that Jun Oh is a ghost.

Min Oh reveals his true intention and pushes Young Hwa off a cliff to save his brother. Jun Oh manages to save Young Hwa and learns that Min Oh was behind it. Min Oh finally realizes what Chul Hwan was after all this time. Meanwhile, Young Hwa finds out that she'll die young because of the curse. 

Young Hwa is confused as Chul Hwan tells her that the curse started because of her. She tells Jun Oh about Chul Hwan, but Jun Oh also doesn't have a clue. In her dream, Young Hwa finally finds out how Do Ha died, and why she had to kill him. Meanwhile, Chul Hwan meets Yi Seul who has been kicked out of her agency. 

Young Hwa knows everything now, and she tells Jun Oh why she had to kill him in the past. She wants to leave him saying they shouldn't be together, but Jun Oh tells her how he feels and asks her to stay. Meanwhile, Yi Seul suddenly appears and tries to kill Young Hwa. Her attempt fails, but Na Yeon gets hurt instead of Young Hwa. Young Hwa feels sorry for the people who got hurt because of her. 

Young Hwa and Jun Oh tell their friends everything and ask them for help. Jun Oh tries to find a way to stop So Ri Bu and end the curse. Chul Hwan tricks Young Hwa to come to the hospital where Min Oh is hospitalized. He threatens her with Min Oh's life, but she uses her amulet to stop him. Jun Oh arrives just in time to save her, and Chul Hwan tells Jun Oh everything about the curse.

Chul Hwan finds Young Hwa and Jun Oh hiding in a secret cabin with their friends. Min Oh appears just in time with the amulet, but Chul Hwan defeats him and finally gets a chance to kill Young Hwa. However, Jun Oh stops him, and Chul Hwan disappears. Since Jun Oh has completed his mission of saving Young Hwa, he disappears as well.