"Kotaro Lives Alone" centers on Kotaro Sato, a precocious four-year-old boy who moves into an apartment complex and lives independently. Despite his young age, Kotaro displays remarkable maturity, intelligence, and self-sufficiency, managing daily tasks such as cooking, cleaning, and budgeting with surprising competence. His neighbors, initially puzzled by his situation, gradually become involved in his life, offering support and forming bonds with him.

The narrative unfolds through Kotaro’s interactions with the residents of the apartment complex, particularly his next-door neighbor, Shin Karino, a struggling manga artist. Karino becomes a central figure in Kotaro’s life, often stepping into a quasi-parental role, though Kotaro’s independence frequently challenges Karino’s assumptions about caregiving. Other neighbors, including a former yakuza member, a kind-hearted woman, and a mysterious man, also play significant roles, each contributing to Kotaro’s daily experiences and personal growth.

Kotaro’s backstory is revealed gradually, shedding light on the circumstances that led to his solitary living situation. Themes of resilience, family, and community are woven into the story as Kotaro navigates the complexities of his life with a blend of childlike innocence and unexpected wisdom. The series balances moments of humor and heartwarming interactions with poignant reflections on loneliness, responsibility, and the importance of human connection.

The characters are portrayed with depth, and their relationships evolve organically, creating a narrative that is both engaging and emotionally resonant. Kotaro’s unique perspective as a child living independently provides a lens through which the story explores themes of adulthood, vulnerability, and the strength found in unexpected places. The series maintains a neutral yet compassionate tone, allowing the characters’ experiences and growth to speak for themselves.