"Wasteful Days of High School Girl" is a slice-of-life comedy manga centered around the daily lives of a group of high school girls in their second year at Asahi High School. The narrative focuses on their humorous, mundane, and often absurd interactions, capturing the essence of adolescence through exaggerated yet relatable scenarios. The story lacks a central plot, instead presenting episodic vignettes that highlight the quirks and dynamics of the characters.

The protagonist, Tanaka, is a self-proclaimed "delinquent" who prides herself on her rebellious image, though her attempts to appear tough often backfire in comedic ways. She is joined by her classmates, including the eccentric and airheaded Nozomu, who frequently misunderstands situations and speaks in nonsensical riddles. The group also includes the studious and level-headed Shiori, who often serves as the voice of reason, and the quiet, deadpan Akane, whose dry humor and mysterious demeanor add to the group's dynamic. Other characters, such as the overly enthusiastic class representative and the stoic teacher, further enrich the comedic interactions.

The manga thrives on its witty dialogue and situational humor, with each chapter exploring different aspects of high school life, from classroom antics to after-school activities. The characters' exaggerated personalities and their reactions to everyday situations drive the humor, creating a lighthearted and entertaining atmosphere. Themes of friendship, individuality, and the awkwardness of adolescence are woven into the narrative, though the focus remains on comedy rather than deep emotional exploration. The episodic structure ensures that each chapter stands on its own, making it easy to pick up and read without needing to follow a continuous storyline.