Kintaro Yajima, the protagonist of the anime, is a man whose life is defined by a dramatic shift from the lawless fringes of society to the rigid structure of the corporate world. His background is essential to understanding his character. Before becoming a salaryman, Kintaro was the formidable and respected leader of a massive motorcycle gang, a bosozoku, which at its peak boasted thousands of members. This past life honed in him a unique set of values and a direct, action-oriented approach to problem-solving. However, his life took a decisive turn when he met and fell in love with a woman named Akemi. He left his gang to marry her, but tragedy struck when Akemi died in childbirth, leaving Kintaro a widower with a young son named Ryu. It is his promise to his late wife to raise Ryu properly and be a good father that fuels his determination to succeed in the legitimate world.

Kintaro's personality is a striking blend of his past and present. He is a free-thinking, easygoing, and highly principled individual who refuses to bow to social pressure or corporate hierarchy. He speaks his mind openly and is never afraid to confront his superiors, acting with a courage and conviction that often treads a fine line between success and failure. This forthrightness splits the opinions of those around him; some find his honest and charismatic nature deeply admirable, while others worry he will encourage irresponsible behavior. Despite his rough exterior and straightforward methods, he possesses a strong moral code and a deep sense of honor, often acting as a rebel with a cause to fulfill his promises and protect those he cares about.

Kintaro's primary motivation is his son, Ryu. His entire journey from gang leader to salaryman is driven by his vow to his deceased wife, Akemi, to provide a stable and honorable life for their child. This promise is the bedrock of his character, pushing him to endure the mundane and often corrupt world of office politics. Beyond his family, he is motivated by a desire to prove that individuals from unconventional backgrounds, often dismissed as outsiders or losers, possess dynamic and inspirational qualities that can challenge and improve a stagnant system.

In the story of the anime, Kintaro is hired by the Yamato Construction Company after he saves the life of its founder, Morinosuke Yamato. His role is that of a disruptive but ultimately positive force within the corporation. Starting in low-level positions, he confronts corruption, takes on powerful rivals, and shakes up the company's "uptight corporate world" with his pragmatic, action-first philosophy. While his methods are often unorthodox, they consistently yield results and expose the flaws in a system built on bribery, tradition, and subterfuge.

Key relationships are central to Kintaro's development and the plot. His bond with the elderly chairman, Mr. Yamato, is crucial, as the chairman sees potential in Kintaro and serves as a mentor and protector. His relationship with his son, Ryu, is the emotional heart of the series, representing everything he is working for. He also develops a significant romantic relationship with Misuzu Suenaga, the owner of a high-class bar and a former politician's mistress, who recognizes his honorable nature. Another key figure is Ryuzo Igo, a cynical and corrupt branch manager under whom Kintaro is forced to work; Kintaro’s unyielding honesty and hard work eventually challenge Igo’s defeatist attitude.

While Kintaro is a man of strong conviction from the start, he does show subtle development. The series uses flashbacks to contrast his violent past as a gang leader with his present as a salaryman, showing how his core principles have been channeled into a new, more constructive path. He learns to apply his street-smart leadership and unwavering courage within the complex arena of corporate takeovers and power battles, proving that his way of dealing with problems is effective even in a business suit. He remains a dynamic and inspirational character who adds spice to the lives of those around him, rather than one who undergoes a fundamental personality change.

Kintaro possesses several notable abilities that stem directly from his background. He is a formidable fighter, a skill from his gang-leading days that he uses to physically confront antagonists when necessary. He is a natural leader with immense charisma, able to inspire loyalty and rally people to a cause, whether they are former gang members or disillusioned office workers. His most defining ability, however, is his unwavering work ethic and his pragmatic, straightforward method of solving problems; he cuts through bureaucracy and social niceties to achieve his goals, whether by forming unlikely alliances or by simply doing the hard work that others have given up on.