A hyper-lethal deep-cover operative raised as an elite weapon who attempts to live a quiet civilian life as a high-performing student at Seoul International High School. Despite his desire for ordinary domestic peace, his lethal instincts and moral obligation to protect his family and classmates repeatedly pull him into violent conflicts. Powers: Master of military CQB, anatomical strike lethality, improvised weapon combat, rapid tactical calculation, advanced situational awareness, extreme pain tolerance, and fluency in psychological manipulation.

Kang Geon’s father, widely feared throughout international intelligence under the codename "Zero." A former legendary North Korean elite operative and black-hat cyber specialist, he orchestrates their family's safety through meticulous information control, blackmail, and surgical covert strikes. Powers: World-class digital infiltration, cyber warfare, strategic planning, counter-surveillance, advanced tactical firearms handling, and ruthless interrogation methods.

A cold, highly calculating female operative from Geon’s past military training batch. Dispatched by the Party to monitor, test, or liquidate rogue assets, she poses as a student while running covert sabotage operations, maintaining an ambiguous dynamic of lethal competition and lingering camaraderie with Geon. Powers: High-speed assassination techniques, concealed bladed weapons mastery, explosives engineering, disguise, and infiltration tradecraft.

A battle-hardened North Korean hardliner and elite military commander dispatched to Seoul to hunt down deserters, enforce state control, and extract valuable sleeper assets by any means necessary, including civilian collateral damage. Powers: Heavy close-quarters combat, heavy weapon proficiency, ruthless tactical leadership, high physical resilience, and urban warfare command.

The intelligent and perceptive daughter of the powerful Samjeong Group chairman. Attracted to Geon's quiet competence and protective nature, she frequently finds herself caught in the crosshairs of corporate kidnappers and political conspiracies. Powers: Chaebol financial backing, high social influence, academic excellence, and sharp deduction skills.

The arrogant son of the South Korean President who initially rules Seoul International High School through political nepotism and bullying. After suffering a swift, humiliating defeat at Geon’s hands, his arrogance shifts into deep wariness and cautious respect. Powers: High-level political connections, private security access, influence over school administration.