"Boku, Otaryman" centers on a middle-aged salaryman named Daikichi Karasuma, who leads an unremarkable life working at a trading company. Despite his mundane existence, Daikichi harbors a secret: he transforms into a superhero named Salaryman K after work hours. This dual identity is not a choice but a curse, as he is compelled to fight monsters known as "Office Evils," which are manifestations of workplace stress and societal pressures. These creatures prey on overworked employees, feeding on their despair and exhaustion.

The narrative explores Daikichi's struggles to balance his ordinary life with his superhero responsibilities. His transformation into Salaryman K is triggered by his own stress and frustration, making his battles deeply personal. The Office Evils he confronts often symbolize real-world issues such as corporate exploitation, burnout, and the dehumanizing aspects of modern work culture. Each encounter forces Daikichi to confront his own vulnerabilities and the systemic problems plaguing society.

Daikichi's relationships with his colleagues and family add depth to the story. His wife, Yui, remains unaware of his secret life, creating tension as he tries to protect her from the dangers of his double identity. His interactions with coworkers, particularly his boss and subordinates, highlight the pressures of corporate hierarchy and the sacrifices demanded by professional life. The series also introduces other characters who become entangled in Daikichi's battles, including a mysterious woman named Kaoru, who seems to know more about the Office Evils than she lets on.

The plot progresses through episodic battles against various Office Evils, each representing a different facet of workplace or societal dysfunction. These conflicts are interspersed with moments of introspection, as Daikichi grapples with the moral and emotional toll of his dual existence. The series blends action, humor, and social commentary, using its fantastical premise to critique real-world issues. The tone shifts between lighthearted and somber, reflecting the duality of Daikichi's life and the broader themes of the story.

As the series unfolds, Daikichi uncovers deeper truths about the origins of the Office Evils and his own role in the conflict. The narrative builds toward a climactic confrontation that challenges his understanding of heroism and the sacrifices required to effect change. Through its exploration of work-life balance, societal pressures, and personal identity, "Boku, Otaryman" offers a unique perspective on the struggles of modern life, wrapped in the guise of a superhero tale.