Main •
Kang Daniel as Wi Seung-hyun, a passionate youth who cannot stand seeing injustice, he aims to follow in the footsteps of his father who is the
head of the
Gyeonggi Dongbu Police Agency. He places first on the college entrance exam on his second attempt. •
Chae Soo-bin as Go Eun-kang, is active and courageous, she is a troublemaking freshman who enters the police force to chase after an unrequited love and manages to enter the police university after being rejected at first. •
Oh Ah-rin as young Go Eun-kang. •
Lee Shin-young as Kim Tak, a freshman from the junior national judo team who embodies the spirit and passion of youth, is accustomed to being alone but Wi Seung-hyun becomes his one true friend. • Choi Yoon-woo as young Kim Tak. •
Park Yoo-na as Gi Han-na, a freshman who is self-reliant and a realist with a unique prideful charm, does not miss on ranking first place in the department. Her individualistic tendency creates tension with other students who value group life.
Supporting Students • Park Sung-joon as Yoo Dae-il, a "pure macho" freshman, he considers himself a successful
police drama fan because he decided to become an officer after watching
Signal, and passes the entrance exam after three tries. •
Min Do-hee as Woo Ju-young, a freshman from a science high school who dreams of becoming a
forensics investigator. •
Kim Woo-seok as Seo Bum-ju, a sincere and upright freshman who sometimes has excessive thoughts and worries that reveal a timid side; he is meticulous with planning and has unexpected dance skills. • Cheon Young-min as Shin A-ri, an
ulzzang freshman who is interested in fashion and appearance; has a gloomy image, but in actuality has a soft personality and gradually grows closer to her classmates. • Park Yeon-woo as Jang Ju-chan, a fourth-year student, president of the student council, and Go Eun-kang's first love. •
Chung Su-bin as Baek Sun-yu, head of the female student dormitory is also active in school activities, such as training and student council. • Kim Seung-ho as Pyo Hyun-seok, the head of public relations at the police academy, is friendly and buys food for the juniors but has a dark secret. •
Lee Joon-woo as Um Hyuk, a strict principled upperclassman and the head of the police academy's education team in charge of training new students. •
Seo Bum-june as Choi In-sik.
Faculty •
Kim Sang-ho as Cha Yoo-gon, a witty
police science professor who as a police officer had run wild in the past without fear of the world before an incident changed his outlook on life. •
Seo Yi-sook as Kim Soon-young, the university
dean. • Choi Woo-ri as Bang Hee-sun, the charismatic
criminal psychology professor. •
Kang Ae-shim as dormitory janitor.
Family •
Son Chang-min as Wi Gi-yong, Wi Seung-hyun's respected father who is a high ranked police officer. • Ji Soo-won as Oh Sook-ja, Wi Seung-hyun's mother with an extraordinary affection for her son. • Son So-mang as Go Mi-kang, Go Eun-kang's older sister and an art graduate student with a pure and honest charm. • Sa Kang as Gi Han-na's mother. • Lee Moon-soo as Yoo Dae-il's grandfather.
Others •
Kim Yool-ho as Chu Man-seok, a heinous character who commits evil acts. •
Hyun Woo-sung as Kang Nam-gi, a passionate detective struggling to find the truth of the case. • Park Ji-hoon as one of the bullies at the
billiard hall. • Lee Woo-je as one of the bullies at the billiard hall. • Ahn Do Kyu as Hong Yoon-ki, the part-time employee being bullied at the billiard hall. •
Kim Kwon as Jo Han-sol, Asia's young leader and CEO of creative start-up investments. • Jung Yeo-Jun as Shin Eui-seok, the chief secretary who follows the dire personal life of Korean-American CEO Jo Han-sol. • Choi Jae-hyun as Min-yong, Wi Seung-hyun's friend. • Park Sang-hoon as Lee Se-hyun, the
fraudster who was a victim of a bigger
scheme. • Lee Se-mi as Min Hae-ji, the flustered woman at the nightclub.
Special appearances •
Kwak Si-yang as Kim Hyun-soo, a fourth-year student at KNPU and Kim Tak's older brother. •
Shin Ye-eun as Jang So-yeon, a freshman who dropped out in the middle of the
orientation program. •
Go Youn-jung as the profile picture for Yoo Dae-il's blind date. • Park Sang-nam as Go Eun-kang's blind date. ==Episodes==