"Fist of the Blue Sky Regenesis" is a continuation of the "Fist of the North Star" universe, serving as a prequel to the original series. The story is set in 1935, during a tumultuous period in Shanghai, where various factions vie for control of the city. The narrative centers on Kasumi Kenshiro, a martial artist and successor to the Hokuto Shinken style, who becomes embroiled in the chaos of the city's underworld. Kenshiro is a calm and composed figure, often referred to as the "Man of 100 Killings," due to his lethal combat skills and his role in maintaining balance in the martial arts world.

The plot unfolds as Kenshiro returns to Shanghai after a long absence, only to find the city overrun by corruption, violence, and the influence of foreign powers. The story delves into the intricate web of alliances and betrayals among the city's criminal organizations, including the powerful Green Gang and the mysterious Black Moon Society. Kenshiro's presence disrupts the fragile equilibrium, as his actions draw the attention of both allies and enemies. His primary goal is to protect the innocent and uphold justice, but his path is fraught with challenges, including confrontations with formidable opponents who wield their own deadly martial arts techniques.

Key characters include Yan Wang, a skilled martial artist and Kenshiro's close friend, who plays a pivotal role in the unfolding events. Another significant figure is Erika, a woman with a mysterious past tied to Kenshiro, whose presence adds emotional depth to the narrative. The series also introduces a range of antagonists, each with their own motivations and connections to the broader conflict in Shanghai. These include Ryuken, a former Hokuto Shinken practitioner with a grudge against Kenshiro, and Fei Yan, a cunning and ruthless leader of the Black Moon Society.

The story is driven by intense martial arts battles, strategic maneuvering, and the exploration of themes such as loyalty, honor, and the cost of power. Kenshiro's journey is marked by his unwavering commitment to his principles, even as he faces increasingly dire circumstances. The series builds on the legacy of the "Fist of the North Star" franchise, expanding its lore while maintaining the core elements of high-stakes combat and moral dilemmas. The narrative is structured to balance action with character development, ensuring that the stakes remain high and the conflicts resonate on both a personal and societal level.