Dear Hongrang

People think it is a doctor’s bounden duty to save a patient’s life. But things are different now. Things are needed to be considered other than saving one’s life. Modern medicine has been developed remarkably, and it is quite possible to save a person's life who is on the verge of death. But we need to think about if prolonging a patient’s life makes the patient truly happy. Cha Yo Han is a promising doctor who needs only 10 seconds to figure out a patient’s condition. While he is gaining his fame with his outstanding skills, he confronts one patient who changes his whole life. Kang Si Young is a doctor with a warm heart. Her family has been doctors for generations. She takes after her mother’s exceptional talent and her father’s high empathic ability. But one day, she suddenly leaves the hospital. After a year later, she goes to the penitentiary to serve as a temporary medical doctor, and she meets a prisoner who was a former doctor. He is a genius who can grasp the patient’s condition within 10 seconds. After meeting him, Si Young’s life totally changes. And the day she comes back to the hospital, she meets the prisoner again, and this time, he is a professor. Doctor John is a human medical drama of anesthetists who seek the cause of mysterious pain their patients suffer, like detectives chasing after a suspect.

Cellphone app Joalarm is created. If someone likes you and they are within 10 meters of you, the alarm for the app rings. The app also shows how many people like you, but the app doesn't reveal specific details on who likes you.

Kim Jo-Jo (Kim So-Hyun) is a high school student. She is pretty and smart. She seems like cheerful person, but her parents died when she was young. Since the death of her parents, Kim Jo-Jo has lived with aunt's family. Living there is not easy for Kim Jo-Jo. She doesn't download the app Joalarm.

Meanwhile, Hwang Sun-O is a popular male student at the same high school where Kim Jo-Jo attends. He is the son of a wealthy family, but he is not loved by his parents. His best friend Lee Hye-Young also attends the same high school. Hwang Sun-O notices that his best friend Lee Hye-Young likes Kim Jo-Jo. Hwang Sun-O wants to know if his friend really likes her, so he kisses her.

Lee Jae-Sang (Rain) is a lawyer at JK Law Firm, which is one of the biggest law firms in South Korea. He is an excellent lawyer, but he only cares about winning for his benefit. One day, he has a mysterious car accident and he is drawn into a parallel world. There, Lee Jae-Sang finds himself working as a prosecutor. He is strict in carrying out the law. He is married to Ra Shi-On (Lim Ji-Yeon), who loves Lee Jae-Sang and is faithful to him. In the world where Lee Jae-Sang came from, he broke up with Ra Shi-On ten years earlier and Ra Shi-On works as a detective. Lee Jae-Sang struggles to cope with his different selves.

Eun Dong-Joo attempts to get back her stolen life. When she was 6 years-old, she was abandoned at an orphanage. She did not remember anything except her name. Despite her difficult environment, she has grown into a woman with a positive and bright personality.