Ahn Go-eun

Nags Park Jin-eon and Choi Kyung-goo. Former high school student. Current hacker. Refers to Kim Do-gi as Driver Kim Do-gi, Park Jin-eon as Mr. Park, Choi Kyung-goo as Mr. Choi, and Jang Sung-chul as Director.

Park Jin-eon

Gets lectured by Go-eun. Former researcher at the Korea Aerospace Research Institute's Launch Vehicle Technology Department. Current engineer. Refers to Go-eun as Go-eun, Kim Do-gi as Driver Kim, Choi Kyung-goo as Hyung-nim, and Jang Sung-chul as Director.

Choi Kyung-goo

Gets lectured by Go-eun. Former member of the New Vehicle Development Team at Roan Motors. Current engineer. Refers to Go-eun as Go-eun, Kim Do-gi as Driver Kim or Mr. Kim, Park Jin-eon as Jin-eon, and Jang Sung-chul as Director.

Jang Sung-chul

Chairman of the Blue Bird Foundation. Former businessman. Current CEO of Rainbow Transport. Refers to Go-eun as Go-eun, Kim Do-gi as Mr. Kim, Choi Kyung-goo as Mr. Choi, and Park Jin-eon as Mr. Park.

Ahn Young-sook

A doctor whose license was revoked, but she changed her name and opened a new hospital.