"Yoiko" is a comedic anime series that revolves around the daily lives and misadventures of three young girls attending elementary school. The main characters are Miyoko, a cheerful and somewhat naive girl; Kenta, a tomboyish and energetic child; and Midori, a quiet and reserved girl who often serves as the voice of reason among the trio. The series is episodic in nature, with each episode presenting a self-contained story that highlights the girls' interactions with each other, their classmates, and their teachers.

The narrative often focuses on the girls' attempts to navigate the challenges of childhood, from dealing with school assignments and rivalries to exploring their imaginations through play. Miyoko's optimistic and sometimes clueless nature frequently leads to humorous situations, while Kenta's boldness and Midori's cautiousness create a dynamic balance within the group. The series also features recurring adult characters, such as their teachers and parents, who add to the comedic and sometimes chaotic atmosphere.

The humor in "Yoiko" is largely derived from the exaggerated and absurd situations the characters find themselves in, as well as their over-the-top reactions. Despite the comedic tone, the series occasionally touches on themes of friendship, growing up, and the innocence of childhood. The simplicity of the plot and the relatable nature of the characters make the series accessible to a wide audience, particularly those who enjoy lighthearted and nostalgic portrayals of school life.