Introverted Boss

Eun Hwan-ki, the cold and timid CEO of Brain public relations firm. He avoids people as much as possible by hiding out in his penthouse office or covering himself in a black hoodie. Park Ha-joon (ko) as young Eun Hwan-ki

Top Star (Ep. 1)

Ro-woon's mother

Chae Ro-woon, an outgoing rookie employee who is surprisingly silent at home despite her extroverted nature and excellent communication skills She aims to take revenge on her boss for the death of her sister.

Kang Woo-il, the warm and confident, yet sensitive vice-chairman of Brain public relations firm. He is Hwan-ki's close friend and fiancé of Eun Yi-soo. Lee Tae-woo as young Kang Woo-il

Rose Airlines CEO (Ep. 7)

Won-sang's friend

Actor Hwang Young-kyu

Park Ae-ran, Hwan-ki's mother

A presenter

Director Park

Eun Bok-dong, Hwan-ki's father

Dang Yoo-hee, a working mother

Kim Gyo-ri, an employee who has crush on Se-jong

Yu-hui's husband

Woo Gi-ja, Ro-woon's neighborhood brother and a reporter

Scrubber in Korean Spa (Ep. 2), Choir conductor (Ep. 4) and Orphanage Event MC (Ep. 6)

Chae Won-sang, Ro-woon's father

Restaurant Owner (Ep. 4)

Brain security

Eun Yi-soo, Hwan-ki's sister who serves as chaebol heiress and is introverted like him. She has mental illness that was initially instigated by her father's long verbal and emotional abuse of her older brother. Seo Eun-sol (ko) as young Eun Yi-soo