Main •
Kim Hye-soo as Sim Eun-seok, a stern judge of the Juvenile Court with a bitter past that shaped how she perceived juvenile offenders •
Kim Mu-yeol as Cha Tae-joo, a compassionate judge of the Juvenile Court with a past history as a victim of domestic abuse and being in juvenile reformation center. He believes in giving second chances to juveniles as he views them as redeemable as a result of his juvenile past •
Lee Sung-min as Kang Won-jung, chief of Juvenile Justice Division •
Lee Jung-eun as Na Geun-hee, who succeed Kang Won-joong as chief of the Juvenile Justice Division. She is the polar opposite of Eun-seok regarding their stance towards the sentencing of juvenile offenders
Supporting Juvenile Offenders •
Lee Yeon as Baek Seong-woo, conspirator in the Yeonhwa Elementary School Murder Case. • Hwang Hyeon-jeong as Han Ye-eun, the main culprit in the Yeonhwa Elementary School murder case. • Jo Mi-nyeo as Woo Seol-ah, a juvenile pickpocket criminal •
Shim Dal-gi as Seo Yu-ri •
Song Duk-ho as Kwak Do-seok, a driver involved in the minor unlicensed driving accident (episodes 7, 8). • Kim Do-gun as Seo Dong-gyun • Kim Jun-ho as Kang Shin-woo, Kang Won-joong's son involved in exam cheating cases. •
Lee Bom as Gyu-sang's wife •
Lee Seok-hyung as Lee Nam-kyung, a boy who goes to court in a traffic accident case without a license for minors. • Kim Gyun-ha as 'Baek Do-hyun', a brutal juvenile criminal leader. At age eleven, Do-hyun and his friend Hwang In-jun murdered Shim Eun-seok's son Nam-goong Chan but were acquitted of the crime; he and In-jun both later appear in court for a sexual offence.
Victim's parents and offenders • Song Duk-ho • Kim Chan-hyung as Ji-hoo's biological father •
Park Bo-kyung as Ji Hoo's mother • Kim Do-geon • Jang Dae-woong
Yeonhwa District Court • Park Ji-yeon as Woo Soo-mi, director of the Juvenile Criminal Compromise Unit •
Lee Sang-hee as Joo Young-sil, officers involved in juvenile criminal deals. •
Shin Jae-hwi as Seo-bum, executive officer of the Juvenile Criminal Agreement • Keum Kwang-sun as Han Kyung-Jung, judicial police inspector under the Ministry of Justice
Pureum Youth Recovery Center •
Yeom Hye-ran as Oh Seon-ja, director of Pureum Youth Recovery Center. • Jung Yi-soo as Kim Ah-reum, Oh Seon-ja's daughter and Kim Ah-jin's older sister. • Park Chae-hee as Kim Ah-jin, Oh Seon-ja's daughter and Kim Ah-reum's younger sister. • Kim Bo-young as Choi Young-na •
Yoon Seo-ah as Go Hye-rim • Choi Ji-soo as Oh Yeon-ji •
Jo Yoon-su as Yoon Eun-jeong • Ha Yi-an as Woo Min-kyeong • Kim Jung-yoon as Yeo Ji-eun • Cho Hyun-seo as Han Min-joo
Others •
Kim Joo-hun as Namkoong Yi-hwan, prosecutor of the Supreme Prosecutor Office and Sim Eun-seok's ex-husband. • Kim Young-ah as Heo Chan-mi, a member of Geobo Law Firm and lawyer in charge of Han Ye-eun and Shim Eun-seok, a classmate of a training academy. •
Park Jong-hwan as Go Gang-sik, police officers dealing with cases of violence against children, women, youth and domestic violence •
Yoo Jae-myung as Um Joon-gi, an assemblyman • Park Jung-yoon as Do Yoo-kyung • Shin Yeon-woo as Chi-hyeon, a detective in the female youth division. She solves child cases together with Go Kang-sik, the head of the department. •
Chung Su-bin as Baek Mi-joo, a young criminal in an unlicensed hit-and-run case. • Jeon Guk-hyang as Yoo Hye-sun ==Production==