Ji Jin-hee

Han Jeong-hyeon/Lee Suk-kyu Yeon Woo-jin as young Han Jeong-hyeon/Lee Suk-kyu

Han Jeong-woo Ahn Ji-ho as teen Jeong-woo

Baek Soo-hyeon Park Sang-hoon as young Baek Soo-hyun

Park Mu-jin, Acting President of the Republic of Korea, formerly Minister of Environment and chemistry professor at KAIST. He is the show's counterpart of Tom Kirkman.

Kang Tae-wook, a former prosecutor now working as a public defender.

Go Sang-sik

Choi Jin-eon

Young-shik (ep 4-5)

Lee Jae-wook

Yoo Jae-hak

Seon Jung-nam, Min-young's F-ranked client at her old agency (ep. 1)

Kim Yoon-sung

King Sukjong

Jo Jae-hee

: actor, Ma-ri's ex-boyfriend (cameo, ep 8)

Oh Tae-suk

Go Eun-ho

Park Mu-yeol

Min Jeong-ho

Jung Woo-jin

Han Tae-suk (Yu-mi's boyfriend)