The One and Only (South Korean TV series)

• Kim Kyung-nam as Min Woo-cheon[4]

A man at the bottom of his life who gets entangled in a murder case with Pyo In-sook.

• Ahn Eun-jin as Pyo In-sook[5]

A terminally ill woman who is so insensitive to life that she does not know what emotions to choose after being sentenced to death.

• Park Soo-young as Seong Mi-do[6]

An SNS influencer who has been diagnosed with a terminal illness and is faced with an impending end to her glamorous life.

• Kang Ye-won as Kang Se-yeon[7]

A housewife who has led an ordinary life with reasonable expectations and responsibility without being noticed by anyone. She realizes the importance of the stability she trusted so much after being diagnosed with a terminal illness.

• Han Kyu-won as Gu Ji-pyo[8]

A third-generation chaebol, planning director of the Eunkang Group, and boyfriend of Seong Mi-do. He is a hot-headed person who communicates with the public through YouTube with a personality that is so easy-going that even his friends do not know that he is a chaebol.

• Do Sang-woo as Cho Shi-young[9]

A detective from the Metropolitan Police Department of the Seoul Metropolitan Police Agency.

• Go Doo-shim[10]
• Han Gyu-won as Oh Young-chan[11]

Kang Se-yeon's husband. He runs his own business after marrying Se-yeon. Oh Young-chan lives a stable life, however his life slowly begins to fall apart when his wife is diagnosed with a terminal illness and enters the hospice ward.

• Kim Soo-hyung as Lim Ji-hoo[12]

His mother suffers from ALS.

• Jang In-seop as Oh Jin-kyu, detective[13]
• Ahn Chang-hwan as Shin Tae-il[14]

He has a cautious personality and is an ally to Min Woo-cheon, who is a strong and cold-blooded killer.

• Jeon Soo as Ho-seon[15]

She is the "best friend" of Seong Mi-do but beyond appearances they do not have a good relationship and are not close to each other. She attracts attention due to being an influential person.

• Jang Hyun-sung[16]
• Baek Hyun-jin[16]
• Lee Soo-mi[16]
• Yoon Bo-ra as Veronica, the nun for patients in hospice.[17]

Park Sung-hoon was initially cast as Min Woo-cheon however he stepped down from the series on July 14, 2021, due to scheduling conflicts and personal reasons.[18]

On October 25, 2021, it was reported that Kang Ye-won was in self-quarantine after contracting COVID-19 after performing a self-test while she was not scheduled for filming as part of the production recommendation. All personnel who had come in contact with her tested negative, with filming proceeding as scheduled.[19]

On December 6, 2021, it was reported that a staff member had contracted COVID-19 since December 4, 2021, filming was canceled the same day. Later, the staff and actors tested negative. and no additional confirmed cases Therefore, we plan to continue filming that day and continue on schedule.[20]