"Kodomo Keiji Memetan" centers around Memetan, a young and eccentric detective who, despite his childlike appearance and demeanor, possesses exceptional deductive skills. The series blends comedy, mystery, and lighthearted adventure as Memetan tackles various cases, often involving bizarre or whimsical scenarios. His unconventional methods and quirky personality set him apart from traditional detectives, creating a unique dynamic in each investigation.

Memetan is accompanied by his loyal but often exasperated assistant, Koro-chan, a talking dog who serves as both a foil and a partner in solving cases. Together, they navigate a world filled with eccentric characters, from mischievous criminals to peculiar clients, each case presenting its own set of challenges. The narrative often juxtaposes Memetan's childlike innocence with his sharp intellect, highlighting his ability to uncover truths that others overlook.

The series is episodic, with each chapter or volume focusing on a self-contained mystery. These range from solving thefts and uncovering hidden treasures to unraveling strange phenomena. Despite the comedic tone, the stories occasionally delve into themes of morality, justice, and the importance of understanding others. Memetan's interactions with those around him often reveal deeper layers to the seemingly simple cases, adding emotional depth to the otherwise lighthearted narrative.

Supporting characters include recurring figures such as Inspector Megane, a more traditional detective who frequently clashes with Memetan's unorthodox approach, and various townspeople who seek Memetan's help. The series maintains a balance between humor and mystery, ensuring that each case remains engaging while showcasing Memetan's unique charm and ingenuity. The blend of absurdity and clever storytelling makes "Kodomo Keiji Memetan" a distinctive entry in the detective genre, appealing to readers who enjoy both comedy and puzzle-solving.