Choco Mona! centers on the Katori household, where the arrival of three-year-old niece Monaka turns everyday life upside down. Monaka is a precocious and innocent child whose spontaneous words and actions constantly bewilder and delight her family. The story primarily follows Chiseko Katori, Monaka’s aunt and a university student, who is often placed in charge of her energetic niece. Despite the chaos Monaka brings, her charm melts everyone’s heart, and the family—including Chiseko’s parents—finds themselves utterly captivated by her. The manga is a slice-of-life comedy told in four-panel format, emphasizing the warm, humorous, and slightly chaotic bond between a young child and the adults around her. Each chapter presents short, self-contained episodes highlighting Monaka’s unfiltered perspective on the world, her mischievous antics, and the tender moments that arise from her interactions with Chiseko and the rest of the family.