Supporting
Park Ju-won as Ahn Na-hee
A student of class 2–3, who is not so easily adapting to the Mafia game. being more on the soft and shy side, she often gets talked over or ignored by her friends, so she never really argues back. Being on the softer side, she can barely stay afoot as students and friends all around her start dying horrifically. her role as the police makes her feel even more guilty as she wishes she uses her abilities to help in the investigation better.She has a sweet crush on a fellow classmate and friend of hers, Jang Hyeon ho. Hyeon ho being on the athletic and more popular side, she cant help but blush when they interact. But her world crumbles apart when one night he dies right infront of her eyes.
Oh Jung-taek as Cha Yoo-joon
A student of class 2–3, who is dating Ji-soo and the one who tries to protect himself and Ji-soo. Being the more passive one in the relationship, always letting her take charge, he is seen as a coward most of the time, so on his final nights, he decides to make it right. Despite his special role, he makes selfish decisions throughout the game out due to him fearing for his life, which he later regrets deeply especially when someone close to him is killed.
Kim Min-seo as Choi Joo-won
A bullied student of class 2–3. A Friend of Jin Da beom, being a fellow victim of kyung Jun's bullying antics.
Seo Dong-hyun as Park Woo-ram
A student of class 2–3, whose hobby is filming and taking photos and has a crush on Lee Joo-young. He has a more silly and fun personality, being best friends with Hyeon-ho and Jun-hee. He tries his best to defy the role that was given to him by the game, but theres nothing he can do to stop it, which almost crushes him as he feels his friends support, who are unaware of his dark secrets.
Chun Young-min as Park Ji-soo
A student of class 2–3, who is dating Yoo-jun. Her personality can be described as more domnimant and feisty as well as stubborn, especially when it comes to standing her ground for herself and Yoo joon. Making her a target for quite a few people's hatred.
Song Byung-geun as Im Eun-chan
A student of class 2–3. He is the leader of a band club at Yooil High School and yeon-woo's best friend. Having a more fun and light hearted personality, Yeon woo's goofyness rubbing off on him and always making him laugh. He sees his other best friend Eun ha like a little sister, and her death absolutely breaks the trio into shambles.
Kim So-hee as Baek Eun-ha
A member of the band club from class 2–3 at Yooil High School. Friend of Eun chan and Yeon woo, fellow members of the band club, she sees them as her older brothers and hangs out with them all the time, making them more protective over her.
Park Yoon-ho as Heo Yool
A member of the band club from class 2–3 at Yooil High School. Known as the class clown, being the absolute biggest prankster and crazy goofball of the class. but also becoming the first target of the game. Him and Eun ha always had a bit of tension, some say it was friendly, some say it was more then that. which causes her to be a suspect for his death
Hong Sung-pyo as Nam Yeon-woo
A member of the band club from class 2–3 at Yooil High School and Eun-Chan's best friend. He can be described as fun and silly, always making others laugh.
Kang Seol as Choi Mi-na
A member of the dance club from class 2–3 at Yooil High School and Joo-young's best friend.
Kim Gyu-bin as Lee Joo-young
A member of the dance club from class 2–3 at Yooil High School and Mi-na's best friend.
Hong Min-gi as Jang Hyun-ho
A member of the basketball club from class 2–3 at Yooil High School. He is Dong-hyun and Jun-hee's best friend and the one who always looks out for his class mate and friend Ahn Na hee, who he has slight feelings for. He's known as a confident and righteous captain, always being others strength even at his weakest, showing his true care, nobility and selflessness. He's one of the only who can stand an actual ground alongside Jun-hee against Goh Kyung jun's group. which ends up not being very favourfull for him.
Do Byeong-hun as Kim Dong-hyun
A member of the sports club from class 2–3 at Yooil High School and Hyun-ho's best friend. Unlike Hyeon ho, Dong-hyun is more on serious and stoic side, not as welcoming as Hyeon ho which balances them out. He also becomes friends with Jun-hee and Woo-ram through their mutual friend Hyeon ho.
Park San-eun as Shin Seung-bin
A member of a violent group of bullies led by Lyung-jun at Yooil High School. Out of the three, he's definitely the more aggressive type, always picking on Jin ha who he sees as inferior. such great friends, arent they?...
Bae Jae-young as Kim Jin-ha
A member of a violent group of bullies led by Kyung-jun at Yooil High School. Out of the three, he's on the more cowardish and emotional type, though as if he doesnt actually wanna do what he does, showing he has at least some morals, but no will to back them up.