Original: 단, 하나의 사랑
To regain his place in Heaven, a mischievous angel must find love for a cold-hearted ballerina – but he ends up falling for her.
Yeon Seo receives an invitation letter to the 20th anniversary party of Fantasia Cultural Foundation. On her way to take a walk, she hears Seung Hwan talking to the doctor on the phone. She asks the doctor if she can receive the cornea donation. Dan accidentally encounters Yeon Seo and observes her.
Dan goes to Yeon Seo’s place to find his handkerchief. Yeon Seo decides to go to the Fantasia’s party. At the party, Yeon Seo realizes that everyone is looking at her with pity. On the way back home, Yeon Seo and Seung Hwan get in a car accident, and Dan witnesses it.
Dan saves Yeon Seo, but this insubordinate act angers his deity. Dan is in danger of being dissipated, but he gets one last chance. Meanwhile, Seung Hwan dies because of the car accident, and Yeon Seo gets to receive his cornea transplant since Seung Hwan had arranged it with Yeon Seo in advance.
Kang Woo joins the Fantasia Ballet Company as an artistic director, and he criticizes Ni Na harshly. Kang Woo announces to the ballet company that he will appoint Yeon Seo as the lead ballerina. Dan gets hired as Yeon Seo’s secretary and has a hard time working under ill-natured Yeon Seo.
Yeon Seo sees Dan’s wings, but she thinks that Dan is just a pervert. Kang Woo comes into Yeon Seo’s house, and Dan thinks Kang Woo is the culprit. Kang Woo meets Ni Na on his way home, and they have dinner together. During the meal, Ni Na goes to the restroom, and Kang Woo notices that she went to the restroom to throw up her dinner.
Yeon Seo and Dan go to the columbarium together, and it suddenly rains again. Kang Woo suggests that Yeon Seo should dance again, but she refuses. Yeon Seo gets to know that Kang Woo was the one who saved her on the day of the accident. Ni Na’s family goes to Yeon Seo’s house to celebrate her recovery, but Yeon Seo gets furious.
Dan gets arrested because Yeon Seo reports him for housebreaking. The video of Yeon Seo that Ni Na posted on her SNS becomes the talk of the town. Kang Woo announces to the Fantasia’s board of directors that Yeon Seo will hold the press conference to announce her comeback.
Yeon Seo encounters Dan at the place where they met for the first time, and she asks him to help her to walk on her own. Yeon Seo misunderstands that Dan is in love with her. Meanwhile, Dan tries to help Yeon Seo and Kang Woo spend time together. Yeon Seo successfully walks into the place of the press conference on her own, and Yeong Ja surprises.
After Dan kisses Yeon Seo, it suddenly rains. So Dan leaves Yeon Seo alone and runs away. Yeon Seo promises Kang Woo she will get back in shape within a week. Ni Na confesses her feelings to Kang Woo, but he rejects her. Meanwhile, Dan tells Yeon Seo to forget about what happened between two.
Kang Woo asks Dan if he likes Yeon Seo as a woman. Dan asks Hu if it’s possible for an angel to love someone other than the deity. And Hu tells Dan a story about the angel who loved human 15 years ago. Meanwhile, Yeon Seo keeps practicing even though she hurts her foot, and Dan tries to stop her. At that moment, Yeon Seo asks Dan if he ever liked her.
Kang Woo tells Yeon Seo to go to the Fantasia’s Night to show the sponsors that she is the prima ballerina. Dan obtains a driver’s license to serve as Yeon Seo’s secretary, but his driving skill is poor. Yeon Seo attends the event, and Dan keeps an eye on her to prevent anything bad happens to her.
Yeon Seo makes a disturbance during the Fantasia’s Night. Because of her behavior, the sponsors oppose Yeon Seo’s return to Fantasia. Dan thinks that this is a setup. Meanwhile, Yeong Ja tells Yeon Seo to hand over the entire foundation to her. Dan tells Yeon Seo to give up on everything because he doesn’t want her to be in trouble.
Dan tells Kang Woo that he can’t disappear yet. Yeong Ja gathers the sponsors for a meeting. Yeon Seo attends the meeting and apologizes to the sponsors. Meanwhile, Kang Woo tells the members of the ballet theatre that they will be fired if they don’t show up for tomorrow’s practice.
Yeon Seo helps the corps to do volunteer work at the sanatorium. She tries to show her sincerity to them, so she tries her best. She suggests Kang Woo that he should hold an audition for "Giselle". Ni Na goes to Elena to ask her for help. Meanwhile, Kang Woo gets to know that Dan is an angel.
Dan quits his job as a secretary and leaves Yeon Seo’s house. Hu notices that Kang Woo is not an ordinary human. Yeong Ja tells Kang Woo that he should step down as a panel of the audition, and Kang Woo accepts her suggestion under the condition that the dancers will judge each other at the audition.
Yeon Seo is having a hard time because she keeps thinking about Dan. She can’t even focus on the ballet practice, and Kang Woo worries about her. She gets drunk and goes to the place where she met Dan for the first time. Meanwhile, Dan tries to find the place that he keeps seeing in his dream, and he gets his old memory back.
Yeon Seo has a dream about her childhood friend named Seong Woo, and she goes to the island where she met him for the first time. She asks the villagers if they remember the boy, and she gets to know that the boy died a long time ago. Meanwhile, Yeon Seo and Dan get to meet each other on the island.
Dan promises Yeon Seo that he will come back to her soon. Kang Woo tells Yeon Seo that she can lean on him, but Yeon Seo tells Kang Woo not to cross the line again. Meanwhile, Yeong Ja and Ru Na are trying to win over the dancers to their side. Dan is suspicious of Kang Woo and he trespasses on Kang Woo’s house.
Hu gets to know that Kang Woo is the angel who loved a human. Yeon Seo asks Dan what is the story that he is hiding from her. Kang Woo gets to hear that Ru Na and Yeong Ja bought votes from the corps. Meanwhile, Yeon Seo keeps practicing her dance with Dan the day before her audition.
Dan thinks that there must be a way for an angel to become a human. Ni Na and Yeon Seo both do a great job on the audition. After the audition, Kang Woo tells Yeon Seo that he will wait for her at the restaurant to say something. Meanwhile, Dan tries to talk about his identity to Yeon Seo, and it starts to rain at that moment.
After what happened to Yeon Seo at the rooftop of the ballet theatre, she can’t remember what happened to her that day. Kang Woo is suspicious of Yeong Ja and Ru Na for the kidnapping, but they deny it. Meanwhile, Dan worries about Yeon Seo, so he tells Yu Mi to strengthen the security of the Ivy Mansion.
Yeong Ja gets to know that Ru Na schemed to kill Yeon Seo. Ni Na tells Kang Woo that she will be Yeon Seo’s understudy. Yeon Seo thinks Dan is hiding something from her, so she sneaks into his room. Meanwhile, Dan gets to know that Kang Woo was the angel who fell in love with a human.
Yeon Seo remembers everything, including the fact that she was kidnapped. Yeon Seo asks Dan if he really is an angel, and he admits to it. Meanwhile, Yeong Ja tells Ru Na that she shouldn’t plot anything without telling her first. Yu Mi and Yeon Seo notice that Gwang Il’s phone has been bugged.
Dan asks Kang Woo how he could become a human, and Kang Woo tells Dan that Yeon Seo needs to die in order for him to become a human. Yeon Seo receives Gwang Il’s statement that confesses his wrongdoings by the instigation of Yeong Ja. Meanwhile, Kang Woo tells Yeon Seo that Dan will dissipate like dust because of her love.
Yeon Seo holds an emergency board meeting and tells the supporters that Yeong Ja, Ru Na, and Ki Chun will leave Fantasia. Ru Na begs for Yeon Seo’s mercy, but Yeon Seo tells her that she has no intention of forgiving them. Meanwhile, Dan wants to hear the answer from the deity, but the deity doesn’t respond.
Yeon Seo and Dan go on a picnic to the park where they first met. Yeon Seo wants to marry Dan because she thinks it is the only way for them to be together. Meanwhile, Dan falls down and gets hurt in the park, but his wound doesn’t heal itself as usual. They think this is a symptom of becoming a human and they wait for a rainy day to check if it’s real.
Dan decides to disobey the deity’s will, and he proposes to Yeon Seo. Elena suggests Ni Na that she should hurt Yeon Seo in order to be Giselle. Hu warns Dan and Yeon Seo for the last time, but they won’t listen to him. Meanwhile, Dan goes to see Ru Na and gives her a warning not to hurt Yeon Seo once again.
Kang Woo tells Yeon Seo that it will be meaningless to Dan if she doesn’t exist in this world, and she notices that she should die in order to save Dan. Ni Na announces to her family that she will live by herself from now on, and Ru Na gets furious. Meanwhile, Dan and Yeon Seo’s wedding day comes, and they make a vow of their eternal love.
Ki Joon Soo tries to kill Dan, and Hu saves Dan at that time. Yeon Seo tells Kang Woo that she won’t perform on stage because there is no time left for Dan and Yeon Seo. Dan gets to hear that conversation and tells her that she needs to dance for his sake. Meanwhile, Dan and Yeon Seo get to find Hu’s report at the church and they realize Hu’s innermost feelings.
Ru Na tries to hang herself in prison, so she is taken to the hospital. On the day of Fantasia’s show, Yeon Seo decides to show the most beautiful Giselle in the world to impress the deity. Meanwhile, Ru Na escapes from the hospital and sneaks into the theater. Ni Na tries to stop her, but Ru Na doesn’t care about her.
Yeon Seo loses consciousness after her performance. Yeong Ja and Ki Chun go to the police station to see Ru Na, but Ru Na only concerns about whether Ni Na plays Giselle or not even in this situation. Dan wants to be by Yeon Seo's side, but there is no more time left for Dan. Meanwhile, Yeong Ja and Ki Chun come to Yeon Seo’s hospital to apologize to her.
Yeon Seo comes back to home with Dan, and they spend time together happily. However, Yeon Seo realizes that it is her dream. Dan tells Yeon Seo to live happily without him and bids farewell to her. After her dream, Yeon Seo finally wakes up from a coma. After Dan’s disappearance, Yeon Seo tries to live bravely, but she keeps seeing a hallucination of Dan.
