The serene facade of the 2nd-grade 3 class from Yooil High School is shattered when a seemingly ordinary field trip plunges them into a nightmarish scenario - a twisted mafia game of death. Forced into a harrowing struggle for survival, Ko Kyung Jun, the notorious bad boy, finds himself ensnared in a lethal contest where each decision could mean life or death for him and his friends. As his companions succumb one by one, Kyung Jun grapples with the harsh reality of isolation and the impending threat that shadows their every move. In the midst of this sinister game, Lee Yoon Seo emerges as a beacon of hope. Armed with exceptional observational and reasoning abilities, she becomes the linchpin of an investigation to unmask the mafia, police, doctor, and citizen within their own ranks. Driven by an unwavering determination to both escape and protect her classmates, Yoon Seo navigates the treacherous web of alliances and betrayals. However, Yoon Seo's focus takes an unexpected turn as her old feelings for Kyung Jun, the once-despised bully, resurface. Despite the complexities of her emotions and her prior crush on Kim Jun Hee, her best friend, Yoon Seo can't ignore the danger Kyung Jun faces due to his anger issues. Desperate to save him from elimination, she embarks on a mission to change him for the better, all while suppressing her lingering affection for him. The story unfolds as Yoon Seo endeavors to make Kyung Jun listen, ensuring that he stays by her side until the end of this perilous game, forging a connection that transcends the boundaries of survival.