"Nan kuru Nee-san" is a comedic slice-of-life manga series that revolves around the daily lives of two sisters, Nee-san and Imouto, who share a small apartment. Nee-san, the older sister, is a carefree and eccentric individual with a penchant for bizarre and often nonsensical behavior. Her unpredictable antics frequently disrupt the otherwise mundane routines of their lives. Imouto, the younger sister, is more grounded and responsible, often finding herself exasperated by Nee-san's eccentricities. Despite their differences, the sisters share a close bond, and their interactions form the core of the series.

The narrative is episodic, with each chapter presenting a self-contained scenario that highlights the sisters' dynamic. Nee-san's behavior ranges from the absurd, such as attempting to create a "perfect" sandwich with increasingly ridiculous ingredients, to the surreal, like imagining herself as a superhero battling imaginary foes. Imouto, while often frustrated, occasionally indulges in her sister's whims, leading to moments of genuine camaraderie and humor. The series thrives on its comedic timing and the contrast between Nee-san's chaotic energy and Imouto's more reserved demeanor.

Supporting characters occasionally appear, including friends, neighbors, and acquaintances, but the focus remains firmly on the sisters. These secondary characters often serve as foils or catalysts for Nee-san's antics, further amplifying the comedic situations. The humor is largely situational, relying on the absurdity of Nee-san's actions and Imouto's reactions to them. Despite its comedic tone, the series occasionally touches on themes of family, responsibility, and the quirks of sibling relationships.

The artwork complements the lighthearted tone, with expressive character designs and exaggerated facial expressions that enhance the comedic moments. The pacing is brisk, with each chapter delivering a quick, humorous vignette that captures the essence of the sisters' relationship. "Nan kuru Nee-san" is a straightforward, humorous exploration of sibling dynamics, offering a series of entertaining and often absurd scenarios that highlight the unique bond between its two main characters.