Kojiro Nanjo, widely recognized by his skate alias Joe, commands prominence in the underground skateboarding circuit "S." His origins lie in Okinawa, where he established an enduring kindergarten friendship with Kaoru Sakurayashiki. Their teenage years introduced Ainosuke Shindo (Adam) when Kaoru challenged him to a skateboarding beef, forging an inseparable trio dynamic. Adam's sudden departure to America seven years before the main timeline instilled lasting betrayal, profoundly affecting both Kojiro and Kaoru. Physically imposing with a muscular build and light tan skin, Kojiro displays wavy dark green hair, typically styled with a small section secured in a low ponytail. His features include piercing red eyes and a black sun-shaped tattoo on his left shoulder. Prioritizing comfort for his physique, he favors casual wear like jeans and striped shirts outside "S." At his Italian restaurant, Sia la luce, he dons chef whites. As Joe during "S" competitions, he adopts minimal attire: unzipped jackets exposing his torso, white pants, fingerless gloves, and accessories like neck and waist bands. Kojiro’s personality merges a charismatic, flirtatious facade with underlying loyalty and perceptiveness. Frequent interactions with women at "S" cultivate his playboy reputation, yet this contrasts his role as a steadfast supporter. He consistently tends to Kaoru, aiding him after injuries and hospital visits, while serving as a paternal mentor to younger skaters like Reki Kyan and Langa Hasegawa. He detects Reki’s battles with self-doubt, offering guidance to mend his friendship with Langa. His skateboarding prowess, dubbed "Six-Pack Skater," harnesses raw physical strength. He employs power-centric techniques uncommon in the sport, such as the "Power Break"—a high-velocity turn demanding brute force to lift off walls. He adapts biking maneuvers like the superman position, using core strength to suspend himself aerodynamically without handle support. Dominating "S" races with precise control and endurance, these skills were honed from his teenage years. Professionally, Kojiro owns and operates Sia la luce following culinary studies in Italy. His disciplined routine balances restaurant management, training, and mentorship: early jogs and strength workouts precede lunch and dinner service prep, often concluding with hosting Reki and other skaters at the eatery. Relationships anchor his life. His bond with Kaoru involves perpetual bickering yet unshakable trust; they lean on each other during clashes with Adam and personal trials. He cultivates camaraderie at "S," mediating tensions among younger participants and dispensing pragmatic advice. His exchanges with Reki emphasize his knack for soothing the youth’s anxieties about inadequacy. Trivia highlights include his favorite dish (acqua pazza), hobby (eating tours), and a future-focused yet adaptable outlook. Regarded as the most responsible adult in his circle, he balances lightheartedness with reliability.