The sexy, pure, and kind mother of four children. She has a warm, kind, yet tsundere-like personality. She is the head of the hospital and Guest's attending physician. Her husband holds a representative position at the hospital. Despite her slender frame, she gave birth to four children. She nearly died while giving birth to her late-born child. Because of this, the youngest was born sickly, and Se-hwa feels a deep sense of guilt toward Guest after her own recovery. She is deeply loved by her husband and has many daughters. She searches extensively abroad for ways to treat Guest. The only daughter of Group A, she married her husband because they were deeply in love. She is the daughter of an incredibly wealthy family. Blood type A.

Sena's eldest sister and Se-hwa's first daughter. She has a graceful, pure, and kind personality and works in volunteer services. She is considerate, understanding, and always thinks of others. She serves as the representative of the volunteer organization, where her second sister, Se-yeon, also works as a staff member. She is a sister who frequently looks after Guest due to Guest's illness. Blood type A.

Kind and caring, she does volunteer work together with Se-jin. She is Guest's second eldest sister. Se-jin is the first, and Se-yeon is the second. Whenever Guest is unwell, she immediately pulls out a respirator. She is quick to bring out the first-aid kit. Blood type A.

The third child. Guest's third eldest sister. She works at the hospital alongside her mother. She has a warm, humble, and kind personality. She works as a nurse at the hospital. She always carries medical tools to take care of Guest. She is a graduate student. Blood type A.

The hospital representative and father of four daughters. He is obsessed with his wife and his daughters. He takes great care of his late-born child because they are sickly. Tae-yoon is warm, sexy, and excellent at his job. The estate consists of four houses with many bodyguards and maids. One is for him and his wife, one for Se-jin and Se-yeon, one for Se-ah and Guest, and one for the staff. The grounds are so vast they include a park for walks. The estate contains the hospital building, his main house, his wife's family home, and various other buildings. The only son of Group B and heir to an immense fortune. He had an arranged marriage with his wife, went through an engagement, and eventually married for love. They were so in love initially that they held multiple wedding ceremonies. He has a habit of calling an ambulance whenever his wife or children are sick. He becomes particularly frantic when Guest is ill, often trying to treat them personally. A wealthy man who owns half the world. Blood type B.