Born as the late child of a nouveau riche family, she had a luxurious childhood. During her school years, she spent a gloomy adolescence as the top student in every subject, eventually securing her 'Medical School Acceptance Letter'. She is self-centered. From her uncontrollable mouth to her raw facial expressions that she doesn't bother to manage at all—in short, she is a failure and unqualified for social life. She endured six years of med school because her father promised to let her live independently, and she forced herself through her internship because he promised to open a clinic for her. The moment all those promises fell through, she left Jongno Yulje Hospital without a second's hesitation and became the subject of notorious rumors while drifting between hospitals. Now, that same Oh I-young has returned to Jongno Yulje! And to the Department of Obstetrics and Gynecology, which she swore she'd never go to! They say people don't change, and she is as consistent as ever. She still carries a cynical and indifferent personality, constantly saying a soulless 'Ah, I see.' She has never had anything she wanted to possess, anything she wanted to do, and lacks desperation, patience, and persistence. As always, she just wanted to live her own day well regardless of others, holding onto the petty mindset of just enduring for the sake of a paycheck. But before she knew it, she started caring about the people in the OB/GYN department at Jongno Yulje. Even as she habitually grumbles, 'I won't do it! I can't! I'm quitting!', I-young heads to the hospital at 5:30 every morning with the most indifferent face in the world.

The ultimate fashionista of Yulje who lives and dies for style! Every morning, there is someone who treats the hospital lobby like a runway: first-year OB/GYN resident Pyo Nam-gyeong. He dyes his hair the latest trendy colors at the salon, puts effort into his makeup for the short commute, and cannot give up his luxury necklace even when putting on surgical scrubs. However, he thinks the coolest thing of all is 'himself' in a white gown... ...or so he thought, but style be damned. One day was enough for all his fantasies and delusions to shatter. He thought he would be a resident who commands the ward with his white gown fluttering, but the reality is that he's busy pouting his lips to hold back tears at the sound of a mother's labor pains, a patient's groans, and the professor's scolding.

An idol who led K-culture at the center of the music industry during a certain era... well, not quite. He was a member of the group 'Hi-Boys', who are considered a failed group by some and a 'Sugar Man' by others, having met a glorious end after leaving behind exactly one hit song. His dancing, singing, and even popularity were always last in the team, but thanks to his high IQ and excellent mental calculation skills, he became the 'ending fairy' of quiz programs rather than music shows. After the team disbanded, he utilized that personal talent to focus on his studies and barely managed to enter medical school. He expected applause for being the 'first idol-turned-resident', but what awaited Jae-il was only the title of 'last place' no matter what he did.

A Superman who appears without fail whenever something happens and then vanishes into thin air, he is the resident guardian deity of the OB/GYN department. From professors to interns, everyone is constantly looking for Do-won, so his days pass in a blur. Consequently, all his actions are beyond fast—they are like lightning.

A 'Super AI' type human who would make Bixby cry, finding studying the easiest thing and textbooks the most interesting thing in the world. No one expected that Sa-bi would become the biggest 'hole' among the first-years. Despite memorizing books and papers perfectly, she becomes speechless at a patient's questions, and even when she explains things accurately according to the chart, mothers look at her with total distrust. She needs to have done something wrong to correct it, or made a mistake to apologize for it... but since she doesn't know the reason, she can't do anything, and because she does nothing, she can't help but get scolded.

She is older in spirit than the professors, a so-called 'young old-timer'. She was just waiting for the day she could stop being the youngest in OB/GYN and show off her senior charisma to the first-years, but what on earth?! The 'nowadays' first-years are weirder than she expected. Forget showing respect to seniors like she did! These kids nowadays are far too slack. And that's not all! She's already struggling just to handle the titles of 'second-year' and 'senior', but they don't seem to know or care about her inner turmoil...

A person with a 'sweet and salty' charm who is a wicked witch in March but becomes the 'Professor of the Year' chosen by residents in December. Currently the young professor garnering the most attention in the obstetrics department at Jongno Yulje, handling the most patients, surgeries, and outpatient clinics. One of the things Jeong-min puts her heart and soul into is resident training. She scolds residents for their mistakes with bone-chilling words that bring them to tears, only to feel a bit sorry as soon as she turns away and starts checking their mood to see how to make it up to them. Despite that, if an answer to her question is even a second late, she transforms into a 'question murderer' who pours out follow-up questions until the residents are absolutely sick of it.