Yuki Oshiro Appearance: A dignified young man with black hair shaved at the sides. He wears a black T-shirt with "break through!" printed on the chest and denim shorts. He has red gloves on his hands. Personality: A serious and kind-hearted young man, the typical protagonist type. Background: He has a sickly younger sister. Until last year, he was an ordinary high school student, but after graduating, he began job hunting to pay for her medicine. Unable to find work, he was forced to enter the underground fighting circuit. Combat: A traditional boxer. He steadily wears down opponents with precise footwork, guards, and punches before delivering the finishing blow. Known for his ability to make a comeback, as his spirit never breaks even in dire straits.

Ren Yotsuji Appearance: A defiant-looking boy with short brown hair. Small in stature. He wears an oversized white T-shirt, a baggy coat, leather shorts, and sandals. Personality: A mischievous brat who looks down on others whenever he gets the chance. However, he is a tsundere and a good kid at heart. Background: His parents went bankrupt due to gambling, leaving him to survive the underworld alone. He lived by begging and stealing. His parents suddenly started winning big at gambling later on and began mocking him. He joined the tournament for the prize money to spite his parents and those around him. Combat: High leg strength. He aims for trips or vitals by delivering kicks from an abnormally low stance or jumping from the air. His movements are agile and unsettling, reminiscent of an insect or a beast.

Karen Arisugawa Appearance: Silver bob, blue eyes (colored contacts). She wears a blue and white cheerleader-style outfit with "POP" written in pink on the chest. A blue miniskirt and blue figure-skating-style boots. She wears bloomers underneath, so she isn't bothered if her skirt flips up. Personality: An overbearing and absolute queen, acting as a bratty sadist... because she was told to (she is actually a very good actress). In reality, she is a gentle and shy girl who naturally speaks in polite language. Background: Sponsored by a famous pharmaceutical company, she is essentially the company's puppet. The company's medicine saved her family, so out of gratitude, she acts exactly as she is told despite her hesitation. Combat: Her movements have a rhythm like flowing water. She precisely evades and parries attacks before landing a heavy blow. She can never beat Alan.

Alan Oedo Appearance: Shaved head, muscular build. He wears a gray tank top and red boxer briefs. He has a large scar from a scratch on his left arm. Personality: Boisterous and bellicose. However, he is not violent by nature; rather, he is polite and enjoys looking after others. Background: A former champion of mainstream mixed martial arts. He was expelled from the professional world after accidentally killing a challenger because he couldn't hold back. Having no intention of quitting martial arts, he found his way to the Purgatory Arena. Thanks to him mentoring the younger fighters, the public order of underground fighting has gradually improved, and rule violations have decreased significantly. Combat: A monster of power and durability. He deflects almost all attacks with his muscles and delivers a god-speed lariat as a finishing move when the opponent staggers or tires.