She has long straight hair without bangs and a pretty, puppy-like face. Her mother passed away, and her father lives in Busan. She lives with her in-law Goo Dowon, her sister Oh Juyoung (who is 11 years older), and Juyoung's husband Goo Seungwon. Having been pampered growing up, she has a bit of a sharp tongue and hates working, but she gets everything done once assigned. She is quick to admit her mistakes and correct them, and she possesses excellent manual dexterity. Although she claims she wants to resign every single day, she is the one person who never actually quits. She is a 28-year-old first-year OB/GYN resident. She is in-laws with Goo Dowon but intentionally keeps it a secret at work.

He has short, neat hair and lives in the same house as his in-law, Oh Iyoung. He has an older brother, Goo Seungwon. He has a sharp personality, works efficiently, and is multi-talented, but he is uniquely playful and mischievous only toward Oh Iyoung. While some call him a pushover, he is actually an indispensable presence at the hospital. His manual skills are so good that professors prefer him for procedures. He is a 33-year-old fourth-year OB/GYN resident.

The same age as Oh Iyoung. She has a puppy-like face and a sharp, precise way of speaking and acting. She was ranked first in her entire school and first on the medical school exams, but when it comes to empathy, she is dead last. Since she learned everything from books, she even learned empathy through reading; because she only possesses academic knowledge, she isn't very good at comforting others. She wears a sharp bob cut and glasses. Occasionally, she seems to 'glitch' or malfunction. She is a 28-year-old first-year OB/GYN resident.

Iyoung's OB/GYN colleague who also went to the same high school. She has a puppy-like face with long wavy hair and no bangs. She loves dressing up and is very good at it. Her mother runs a very famous mandu (dumpling) restaurant, and her nickname at home is 'Princess,' though she hides this at the hospital—a secret that would be exposed the moment her mother visits. Her suturing skills are decent, and she is excellent at dressing wounds. She is prone to tears, but not excessively so; she doesn't cry just from being scolded. She is 28 years old.

Iyoung's OB/GYN colleague. He used to be a member of a boy group called 'High Boys.' They even hit number one on music shows, but some call them a failed idol group, and few people recognize him now. While he lacks somewhat in academic background, he is full of persistence and passion. He makes many absurd mistakes at first but grows steadily through study. He has a puppy-like face and neat, wavy hair. He is 28 years old.