Kazuma Kuwabara is a main character in the narrative and begins as the self-proclaimed toughest delinquent at Sarayashiki Junior High School, though he is consistently bested by his rival, Yusuke Urameshi. Despite their constant fighting, Kuwabara is deeply affected by Yusuke's death at the start of the story, and his refusal to accept the loss demonstrates an emotional bond that forms the foundation of their enduring friendship. He leads a small gang of followers, including his friends Okubo, Kirishima, and Sawamura, and operates under a strict personal code of honor that prohibits stealing or extorting money from others.

In terms of appearance, Kuwabara is the tallest member of the main group, standing around six feet tall with a broad, muscular build. He has a distinctive thick red-orange pompadour hairstyle and is typically seen wearing his light blue school uniform, which contrasts with the darker uniforms worn by other male students.

Kuwabara is driven by a strong sense of loyalty, justice, and emotion. He often puts himself in great danger to help others, and his actions are deeply linked to his feelings, such as when he fights inspired by love during the rescue of the ice maiden Yukina. While he is often dismissed as unintelligent, especially by Hiei, he demonstrates considerable emotional intelligence and street smarts. He also has a surprisingly gentle side, with a soft spot for his pet cat, Eikichi. As the story progresses, he shows a dedication to self-improvement, applying himself to his studies and discovering an inner scholar, which allows him to gain acceptance to the high school of his choice.

Kuwabara serves as a loyal ally and the emotional heart of the group. He is the primary human companion to Yusuke, often assisting him on his cases as a Spirit Detective. He maintains a cordial and friendly relationship with Kurama, who often acts as a patient mentor to him. His relationship with Hiei is antagonistic, with Hiei frequently insulting him, though Kuwabara comes to believe that Hiei is a good person underneath his harsh exterior. He is frequently disciplined by his older sister, Shizuru Kuwabara, who is one of the few people to call him by his first name, Kazuma. He falls in love with the ice maiden Yukina at first sight, and though she is initially oblivious to his affection, she cares for his safety and eventually comes to live with his family.

Kuwabara undergoes significant character development, evolving from a simple schoolyard brawler into a powerful fighter who must rely on intelligence and hard work to keep up with his more naturally gifted teammates. He matures emotionally, becoming a dependable figure who is often the most emphatic to the plight of innocent bystanders.

Kuwabara possesses an incredibly high level of spiritual awareness, allowing him to see ghosts and demons and even predict the motives of others. His primary ability is the Spirit Sword, a blade of concentrated spirit energy he can summon at will. He develops this power to wield two swords simultaneously and can extend his blade like a javelin to strike distant targets. During the Dark Tournament, he acquires the Trial Sword, a powerful prismatic blade that also enhances his defense. His most formidable technique is the Dimension Sword, a weapon capable of cutting through space and dimensional barriers, which he unlocks in a moment of intense emotion when his friends are in danger.