• Female • Class of 1999 (Early 40s) • Professor of Neurosurgery (Vice Chair) • A member of the hospital band 'Gongnyong Neungseon,' playing with her 20-year friends every weekend when they have time. • Lives a busy life, earning her the nickname 'The Ghost.' • She attends academic conferences, reviews the residents' papers, always has many surgeries, and is the ace of Neurosurgery. • She has a great personality and looks younger than her age. • She has liked Lee Ik-jun for a long time.

• Male • Class of 1999 (Early 40s) • Professor of Hepato-Biliary-Pancreatic Surgery • A member of the hospital band 'Gongnyong Neungseon,' playing with his 20-year friends every weekend. • Playful, very bright, and has a great personality. • Very popular with patients due to his friendly nature. • A single father raising his 5-year-old son, Lee U-ju, from his previous marriage. • Has a younger sister, Lee Ik-sun, and they have great sibling chemistry. • He liked Song-hwa in college; he tucked those feelings away but is starting to fall for her again. • Has known Kim Jun-wan since middle and high school in Changwon, and they moved up to Seoul together.

• Male • Class of 1999 (Early 40s) • Professor of Cardiothoracic Surgery (Department Chair) • A member of the hospital band 'Gongnyong Neungseon,' playing with his 20-year friends every weekend. • Can be prickly and gets lonely easily, so he lives with Ahn Jeong-won, taking turns paying the utility bills. • Originally from Changwon like Lee Ik-jun; he moved to Seoul for college and occasionally uses his dialect when on the phone. • Blunt and direct with patients, but surprisingly warm and humane.

• Male • Class of 1999 (Early 40s) • Professor of Pediatric Surgery • A member of the hospital band 'Gongnyong Neungseon,' playing with his 20-year friends every weekend. • Kind, very gentle with juniors, smiles often, but is a total cheapskate. • A devout Catholic nicknamed 'Andrea' and 'Buddha.' Among the 99ers, he's called a 'pervert' or 'petty,' but only when he's with them. • Wants to become a priest, but due to strong opposition from those around him, he is eventually giving up on the idea. • Lives with Kim Jun-wan, taking turns paying the utility bills. • Known as 'Daddy-Long-Legs,' he secretly covers surgery costs for those who can't afford them, leaving him constantly broke.

• Male • Class of 1999 (Early 40s) • Professor of Obstetrics and Gynecology • A member of the hospital band 'Gongnyong Neungseon,' playing with his 20-year friends every weekend. • Often expressionless, loves watching 'New Journey to the West,' and is a voluntary loner with zero social life. • Nicknamed 'Dull Bear' or 'Stubborn Bear.' • Appears indifferent, but is actually very considerate of expectant mothers and is the type to stay quietly by their side. • Has a complicated family history: his father had an affair, his mother refuses to divorce, his younger sister passed away, and he is divorced.

• Female • The sole 3rd-year General Surgery resident. • Stoic and extremely direct. • Secretly likes Ahn Jeong-won and keeps asking Lee Ik-jun for help. • Speaks her mind immediately, but has a gentle and cute side in private. • Loves eating and is best friends with Chu Min-ha, often seen together.

• Female • 2nd-year OB/GYN resident. • Persistent, proactive, and a bit clumsy. • Very direct when it comes to romance. • Has a personal crush on the 'Bear,' Yang Seok-hyeong. • Loves tteokbokki. • Views her peer Myung Eun-won as a total fox; she struggles because her workload increases every time Eun-won acts manipulative.

• Male • Chief Resident (4th year) of Cardiothoracic Surgery. • Makes many mistakes and is clumsy, but remains bright and energetic, constantly following Kim Jun-wan around. • A victim of a rental scam, he is in debt and living apart from his beloved wife. • Went through an incredibly difficult process to become a doctor. • Currently preparing for his specialist exam and tends to cause quite a few accidents.

• Female • Medical student intern. • Fraternal twin sister of Jang Hong-do. • Her parents passed away when she was in middle school. • Smiles often, polite, and smart. She is quick to apologize when wrong and is more mature than Hong-do. • As an intern, she is rotating through various departments to gain experience.

• Male • Medical student intern. • Fraternal twin brother of Jang Yun-bok. • His parents passed away when he was in middle school. • Like a bright puppy, he can be a bit slow on the uptake. He is quick to apologize but often stammers and seems more like the younger sibling than Yun-bok. • As an intern, he is rotating through various departments.