Hong Ye-ji as Yoon Young, a 19-year-old girl who is imprisoned for committing a murder[3] Kim Ji-young as Kyung-sook, Yoon Young's hearing-impaired mother Kim Mi-hwa as Soon Je, the senior of Cell 12 Hwang Seok-jeong as Li-ra, a prison hacker Shin Eun-jung as Seon-su, prisoner who loves reading and values principles Jeon So-min as Jang Mi, the last adultery inmate before the abolition of adultery Yoon Mi-kyung an angry troublemaker who appeares as a prisoner in Cell 12 to give Yoon Young hope in life once again Kim Do-yeon as a prison guard[4] Jung In-ki as a prison warden[5] Seo Jin-won as a judge[6] Hong Seo-joon[7] Jung In-gi