"Rappa" is a manga series that centers on the life of Rappa, a young man with a troubled past who becomes entangled in the underground world of illegal street fighting. The narrative begins with Rappa living a life of aimlessness, haunted by the death of his father, a former boxer who was killed in a rigged match. Determined to uncover the truth behind his father’s death and avenge him, Rappa enters the brutal and unforgiving world of underground fighting, where strength, skill, and survival are paramount.

The story unfolds in a gritty urban setting, where Rappa encounters a variety of fighters, each with their own motivations and backstories. Among them is Goki, a seasoned fighter who becomes both a mentor and a rival to Rappa. Goki’s guidance helps Rappa hone his raw talent, but their relationship is complicated by Goki’s own ties to the criminal underworld. As Rappa rises through the ranks of the underground fighting circuit, he uncovers a web of corruption and betrayal that extends far beyond the ring.

Key antagonists include the enigmatic crime lord known as "The Boss," who orchestrates the underground fights and has a direct connection to Rappa’s father’s death. The Boss’s organization is a formidable force, and Rappa must navigate a dangerous path to confront him. Along the way, Rappa forms alliances with other fighters, such as the stoic and disciplined Ryu and the fiercely independent fighter Aya, who becomes a close ally and confidante.

The plot is driven by Rappa’s dual goals of avenging his father and dismantling the criminal network that controls the underground fights. The series explores themes of justice, loyalty, and the cost of vengeance, as Rappa’s journey forces him to confront his own morality and the consequences of his actions. The fights themselves are intense and visceral, showcasing a mix of martial arts styles and raw physicality, with each battle serving to advance the plot and develop the characters.

As the story progresses, Rappa’s resolve is tested repeatedly, both in and out of the ring. The narrative builds toward a climactic confrontation with The Boss, where Rappa must use everything he has learned to achieve his goals. The series balances action with moments of introspection, providing depth to its characters and their struggles. "Rappa" is a story of perseverance, redemption, and the pursuit of truth in a world where the lines between right and wrong are often blurred.