"Kohitsuji Jirushi no Runpappa" centers on the life of Runpappa, a former delinquent turned devoted single father, and his young son, Kohitsuji. The narrative explores their daily struggles and the challenges Runpappa faces as he strives to provide a stable and loving environment for his child. Runpappa’s past as a gang member often resurfaces, complicating his efforts to lead a peaceful life. Despite his rough exterior and history of violence, he is deeply committed to Kohitsuji’s well-being, showcasing a tender and protective side.

The story delves into themes of redemption, parenthood, and societal judgment. Runpappa’s unconventional parenting methods, shaped by his street-smart background, often clash with societal norms, leading to humorous and heartwarming situations. Kohitsuji, a bright and curious child, serves as a moral compass for his father, often highlighting the innocence and purity that Runpappa seeks to preserve in their lives. Their bond is the emotional core of the series, emphasizing the transformative power of love and responsibility.

Secondary characters, including Runpappa’s former gang associates and neighbors, add depth to the narrative. These interactions reveal the complexities of Runpappa’s past and his ongoing struggle to reconcile it with his present role as a father. The series balances comedic moments with poignant reflections on family, resilience, and the impact of one’s choices. Through its episodic structure, "Kohitsuji Jirushi no Runpappa" portrays the evolving dynamics between father and son, offering a heartfelt exploration of unconventional family life.