In 1974 in the suburban town of Shimizu, Shizuoka, the daily life of third-grader Momoko Sakura, a mischievous and dreamy girl everyone calls Maruko, unfolds with her modest family. The live-action series follows the young troublemaker as she navigates the small comedies and dramas of childhood, clashing with her strict but loving mother, being teased by her easygoing father, and enjoying the unconditional adoration of her grandfather, Tomozou. While her older sister, Sakiko, is studious and responsible, Maruko is lazy, often late for school, and prone to getting poor grades, yet her innate optimism and good heart always see her through the everyday conflicts she creates.

The core of the story revolves around Maruko's interactions within her family and her circle of friends at school, including her intelligent best friend Tamae and the wealthy, sophisticated classmate Kazuhiko Hanawa. The narrative focuses on simple, relatable episodes, such as a family car trip that ends in disappointment when they drive all the way to Chinatown only to eat plain noodles after their father wins a car in a lottery. Another notable arc follows the students as they invite their parents to school to observe their classes, leading to a mix of pride and embarrassment for everyone involved. In a particularly touching story, after Maruko falls off her yellow bicycle and scrapes her knee while learning English, her father scolds her for her carelessness, making her deeply sad; however, the next morning, she discovers he has secretly installed a rearview mirror on her bike to keep her safe. Through these small, poignant moments, the series captures the warmth and frustration of post-war Japanese family life.