Irene Bae Joo Hyun

• 35
• Cardiac surgeon 
• Previously worked in Medicine school as a lecturer.
• Before being a lectuer she worked in a different hospital for about a year
• Join Seoul National Hospital (SNH) when she's 30 
• Known to be cool and calm

Kang Seulgi 

• 29
• Neurosurgeon 
• Joined Seoul National Hospital (SNH) at 23
• Has a rather clueless appearance
• Gifted, smart and intelligent (got her PHD training in Med school straight after high school) 

Other characters:

Kim Heechul

• 36
• Plastic surgeon
• Son of new SNH director

Wendy Son Seungwan

• 29
• Pediatric surgeon
• Joined SNH at 24
• Loves children
• Seulgi's Bestfriend and go-to operation assistant 
• Always the peace maker between the two doctors

Joy Park Sooyoung

• General surgeon 
• Irene's friend 
• Flirty; Loves to drink when she's not working 

Kim Yeri 

• Nurse
• Helps out in most of Irene's and Seulgi's operatons
• Friends with the 4 doctors