Kim Gun-woo is a ripped boxer with a muscular, tall build, sharp right-cheek scar, slightly messy black hair, and intense, dark brown eyes that shift from gentle to fiercely focused. He wears athletic gear or boxing wraps. As the primary protagonist, his role is using his lethal boxing skills to navigate the criminal underworld, pay off his mother's debt, and take down a corrupt loan shark syndicate. He is fiercely protective of his mother and kind. He is a former Korean Marine Corps 1,207th class. He is kind hearted, polite, shy and gentle. But strong and stubborn.

Hong Woo-jin is a tall, muscular boxer with an athletic build, short black hair styled in a stylish, upward-swept taper fade, and sharp, expressive dark eyes that radiate a confident, playful energy. He has a charismatic smile and wears colorful casual clothes or sleek leather jackets. As the co-protagonist, his role is to serve as Kim Gun-woo’s fiercely loyal partner, using his tactical wits and agile boxing skills to help destroy the corrupt loan shark syndicate. He has a funny humor. He's from the Korean Marine Crops 1,216th class. Kind and funny

Kim Myeong-gil has slicked-back, short black hair and cold, predatory dark eyes that reflect his sadistic nature. He has a sharp, menacing face with a prominent left-side facial scar, and a tall, imposing build. He dresses in expensive, tailored suits or flashy silk shirts. As the main antagonist and ruthless CEO of Smile Capital, his role is to orchestrate predatory loan schemes, blackmail wealthy targets, and serve as the final criminal boss the heroes must destroy

President Choi Tae-ho is an elderly man who uses a wheelchair due to past paralysis. He has short, graying black hair, deep-set, sorrowful dark eyes, and a weathered, dignified face. He typically wears traditional Korean hanbok or simple, loose-fitting clothing. As a legendary former loan shark turned benevolent billionaire, his role is to act as the primary mentor to the young boxers, financing their mission and providing strategic guidance to take down his former protege.

Cha Hyeon-ju has short, choppy black hair with a messy fringe and sharp, dark, observant eyes that convey her guarded personality. She has a slim, tomboyish appearance and is typically seen wearing dark streetwear, oversized hoodies, or leather motorcycle gear. As President Choi’s fiercely independent adopted granddaughter and investigator, her role is tracking predatory loan sharks alongside the boxers before unexpectedly fleeing abroad late in the season.

Kang In-beom has a short, rugged buzz cut and small, menacing dark eyes hidden behind a permanently scowling face. He has a massive, towering, and heavily muscled powerhouse physique, typically wearing tight t-shirts or dark jackets that emphasize his size. As Kim Myeong-gil’s primary right-hand enforcer, his role is to act as the syndicate's ultimate physical weapon, using his brutal street-fighting strength to overpower and severely injure the protagonists

Lee Doo-young has short, neatly parted black hair and warm, expressive dark eyes that quickly turn lethal in battle. He features a ruggedly handsome appearance, often wearing leather motorcycle jackets. Unlike his old-guard partner Yang-jung, Doo-young is not a former Marine; he served strictly as President Choi’s loyal "left arm" and tactical driver. His role is a fierce motorcycle enforcer who briefly leaves retirement to train the main boxers and safeguard his pregnant wife.

Hwang Yang-jung has short, graying black hair and calm, deeply piercing dark eyes that reveal his decades of combat experience. He possesses a lean, sharp, and physically fit physique, often wearing clean white chef coats or simple casual clothing. As a legendary former fighter from President Choi's old guard, his role is to emerge from his quiet life as a sushi chef to protect his mentor, using his lethal knife-wielding skills to eliminate waves of Smile Capital thugs. And former Marine too

Yoon So-yeon has short, simply styled black hair warm, expressive dark eyes that reflect her loving and hard-working nature. She possesses gentle, maternal appearance, typically seen wearing practical aprons, casual clothing suitable for running her business. As Kim Gun-woo’s devoted mother, her role is the emotional catalyst for the story; her small cafe is targeted and destroyed by Smile Capital's extortionists, trapping her in a predatory debt that forces her son into the criminal underground. She is a very warm, kind hearted woman.

Hong Min-beom is a third-generation chaebol heir who dresses in immaculate, high-end designer business suits and luxury clothing. He has short, neatly parted black hair and dark, expressive eyes that transition from arrogant and entitled to deeply traumatized and intensely vengeful. As a wealthy hotel conglomerate director blackmailed and tortured by Smile Capital, his role is to serve as the strategic financier and ally to the boxers, providing the political backing and resources to shield them.