The First Man

Ham Eun-jung

Oh Jang-mi / Ma Seo-rin

Oh Hyun-kyung

Chae Hwa-young

Yoon Sun-woo

Kang Baek Ho

Park Geon-il

Kang Jun Ho

Kim Min-seol

Jin Hong Ju

Jeong So-yeong

Jung Suk Hui [Jang Mi and Seo Rin's biological mother]

Kim Hak-seon

O Bok Gil [Jang Mi's adoptive father]

Lee Hyo-jeong

Ma Dae Chang [Seo Rin's grandfather]

Lee Ki-chang

O Tae Pyeong [Jang Mi's brother]

Lee Jae-hwang

Lee Gang Hyeok [Hwa Yeong's confidant]

Jung Chan

Kang Nam Bong [Baek Ho and Jun Ho's father]

Kim Sun-hye

Yeom San Wol [Hong Ju's mother]