Zack, also known as the dancer from the team Baron, is a character from the Japanese series featuring armored riders. His background is rooted in street dance and physical combat, as he was originally a member of Team Baron. Initially, he devoted most of his time to fighting as a primary means of survival and expression. However, after encountering a character named Asami, he developed a genuine dream and passion for dancing, shifting his focus away from pure violence.

In terms of personality, Zack is fiercely proud and loyal, particularly regarding his team and its leader, Kaito. He matures from a violence-oriented fighter into a dedicated guardian of his team. His motivations are driven by a desire to protect Team Baron's honor and to pursue his personal growth as a dancer. Even when he does not fully agree with Kaito's radical decisions, he continues to fight to uphold the team's glory and his own sense of responsibility.

Within the story, Zack serves as a secondary rider and the successor to Team Baron. After Kaito decides to leave the team, Zack is entrusted with a mass-produced transformation device and takes over leadership. As the armored rider Knuckle, he fights alongside other main characters against invading forces. He plays a key role in attempting to stop Kaito's extreme plan to betray humanity, though his direct assassination attempt fails, and he also loses in a subsequent fight against Kaito's more powerful rider form.

Key relationships define his development. His bond with Kaito is complex; while he is one of the closest individuals to Kaito, he admits he may never fully understand him. Nevertheless, he vows to continue fighting for Kaito's pride and the team's legacy. His friendship with Asami is instrumental in sparking his love for dance, while his interactions with Peko and others solidify his role as a dependable leader and teammate.

Zack undergoes significant character development, transitioning from a background dancer focused on combat to the leader of his team and a hero. He learns to balance his ideal of dancing with his duty as a rider. After the main crisis in the city resolves, he pursues this balance further by leaving for the United States to train as a professional dancer, symbolizing his commitment to his personal growth and the peaceful pursuit of his art.

Notable abilities include his proficiency in street dance and breakdancing, which translate into agile and acrobatic fighting styles. As the rider Knuckle, he uses a mass-produced transformation device and wears armor that enhances his physical capabilities, allowing him to fight against monster-like adversaries. His fighting style combines his dance moves with powerful strikes, making him a nimble and unpredictable combatant.