Kankichi Ryotsu, nicknamed Ryo-san, is the protagonist of the narrative. Born and raised in Asakusa, Tokyo, his childhood was defined by mischievous antics—hijacking bascule bridges, scaling industrial structures—actions that masked his harmless intentions, often misread by others. These traits followed him into adulthood, cementing his reputation as a troublemaker even after he joined the police force.

Physically, Ryotsu sports a short, stocky frame, a crew-cut hairstyle, thick body hair, and a prominent "m"-shaped unibrow. He typically wears a rolled-sleeve blue police uniform paired with wooden sandals gifted by his superior, Daijiro Ohara. The sandals, given after Ohara arrested him for public drunkenness and later mentored him into police work, symbolize their contentious father-son bond, strained by Ryotsu’s lax work ethic and Ohara’s alternating reproach and pride.

Lazy yet enterprising, Ryotsu shirks patrol duties to pursue audacious yet ill-conceived money-making schemes. His street-smart grasp of Japanese culture, traditional games, and modern trends fuels ventures that frequently spiral into disaster—like damaging Tokyo Tower—though he occasionally displays sharp crime-solving instincts or civic dedication. His relentless pursuit of wealth stems from childhood poverty, contrasting starkly with affluent colleagues Keiichi Nakagawa and Reiko Akimoto, whose global savvy and resources he both covets and manipulates.

Family ties remain fraught, particularly with his hot-tempered father, Ginji, whose volatility mirrors his own. His mother, Yone, mediates their clashes, while his disciplined younger brother, Kinjiro, embodies the success Ryotsu never achieved. At work, he shares an uneasy camaraderie with motorcycle officer Hayato Honda and a combative yet caring dynamic with Ohara, who oscillates between disciplining him and quietly championing his rare triumphs.

A recurring motif is his inadvertent wrecking of property or infrastructure, tallying as "Today’s Damage"—financial penalties underscoring his chaotic, well-meaning essence. These incidents balance his anti-hero persona with sporadic heroic acts fueled by raw strength and tenacity. Across media, his arc weaves consistent growth through failure, adapting core traits to shifting societal landscapes.

In the final narrative, his reckless antics trigger extensive collateral damage, cementing his legacy as a flawed yet indispensable fixture within the police box community. Resolution of his longstanding tensions with colleagues and family highlights themes of redemption and acceptance, anchored by his unyielding embrace of an unconventional life.