"Sun-Ken Rock" is a manga series centered around Ken Kitano, a young Japanese man who travels to South Korea to pursue his childhood crush, Yumin, a police officer. Initially, Ken aspires to become a police officer himself to be closer to Yumin, but his lack of qualifications leads him down a different path. He becomes involved with a local gang, quickly rising through the ranks due to his exceptional fighting skills, strategic mind, and unwavering loyalty. Over time, Ken transforms the small gang into a powerful organization, the Sun-Ken Rock Group, which gains control over various districts in Seoul.

The narrative explores Ken's internal conflict between his desire for a peaceful life with Yumin and his growing responsibilities as a gang leader. Yumin, unaware of Ken's criminal activities, remains focused on her police duties, creating a tension between their personal and professional lives. The story delves into themes of loyalty, ambition, and the moral complexities of power, as Ken navigates the violent and unpredictable world of organized crime.

Key characters include Ken Kitano, the determined and physically formidable protagonist; Yumin, the disciplined and idealistic police officer who serves as Ken's moral anchor; and Taewoon, Ken's loyal and resourceful second-in-command. The series also features a diverse cast of gang members, rivals, and allies, each contributing to the intricate dynamics of the criminal underworld.

As the Sun-Ken Rock Group expands, Ken faces numerous challenges, including rival gangs, internal betrayals, and the constant threat of law enforcement. The story escalates with intense action sequences, strategic battles, and moments of personal reflection, culminating in a high-stakes struggle for dominance in Seoul's criminal landscape. The series balances its gritty, violent tone with moments of humor and emotional depth, creating a multifaceted portrayal of its characters and their world.