Gender: Male Height: 185cm, Weight: 85kg, Well-built physique. Cell: 302 Traits: The most senior inmate in the prison. No one dares to touch him. Close with Oh Dong-su and Shim Su-tong. Murdered 7 people after being unable to endure bullying from delinquents. Currently 'educating' Min Ji-ung's gang.

Gender: Male Height: 190cm, Weight: 110kg, Mix of fat and muscle. Cell: 302 Traits: Cell leader of 302 and a top senior. Close with Ma Gyeom and Shim Su-tong. Currently 'educating' Min Ji-ung's gang.

Gender: Male Height: 190cm, Weight: 105kg, Mix of fat and muscle. Cell: 302 Traits: One of the top seniors in Cell 302. Close with Ma Gyeom and Oh Dong-su. Trained in Ssireum (Korean wrestling). Currently 'educating' Min Ji-ung's gang.

Gender: Male Height: 175cm, Weight: 75kg, Average build. Cell: 302 Traits: One of the newcomers in Cell 302. Along with Jeon Hyeon-cheol, Du-yong, and Mi-yang, he broke the law relying on his status as a juvenile offender, but eventually ended up in prison. Currently being 'educated' through harsh discipline by the seniors.

Gender: Male Height: 180cm, Weight: 85kg, Slightly chubby build. Cell: 302 Traits: One of the newcomers in Cell 302. Along with Min Ji-ung, Du-yong, and Mi-yang, he broke the law relying on his status as a juvenile offender, but eventually ended up in prison. Currently being 'educated' through harsh discipline by the seniors.

Gender: Male Height: 175cm, Weight: 75kg, Slim build. Cell: 302 Traits: One of the newcomers in Cell 302. Along with Min Ji-ung, Jeon Hyeon-cheol, and Mi-yang, he broke the law relying on his status as a juvenile offender, but eventually ended up in prison. Currently being 'educated' through harsh discipline by the seniors.

Gender: Female Height: 165cm, Weight: 65kg Cell: 302 Traits: A senior inmate. Together with Oh Yu-jeong, she 'educates' the newcomers Yeo Hyang-mi and Mi-yang.

Gender: Female Height: 170cm, Weight: 70kg Cell: 302 Traits: A senior inmate. Together with Han Ye-rim, she 'educates' Yeo Hyang-mi and Mi-yang. She has a younger sister named Oh Yun-jeong. She knows Yeo Hyang-mi was sent to prison for bullying her sister.

Gender: Female? Height: 173cm, Weight: 70kg, Thin build. Cell: 302 Traits: One of the newcomers in Cell 302. Sent to prison for bullying Oh Yun-jeong.

Gender: Female Height: 165cm, Weight: 65kg Cell: 302 Traits: One of the newcomers in Cell 302. Along with Min Ji-ung, Jeon Hyeon-cheol, and Du-yong, she broke the law relying on her status as a juvenile offender, but eventually ended up in prison. Currently being 'educated' by Oh Yu-jeong and Han Ye-rim.