"Kaba-Enchō no Dōbutsuen Nikki" centers on the daily operations and challenges of a small zoo, as seen through the eyes of its staff and animals. The protagonist, Kaba-Enchō, is a hippopotamus who serves as the zookeeper, a role that blends humor and responsibility. The narrative unfolds in a lighthearted yet insightful manner, depicting the interactions between the zookeepers and the animals, as well as the animals' perspectives on their lives in captivity.

The zoo is home to a diverse cast of animals, each with distinct personalities and quirks. These include a mischievous monkey, a prideful lion, a timid penguin, and a wise old tortoise, among others. The animals often engage in humorous or poignant conversations, offering a glimpse into their thoughts and feelings about their environment and relationships with humans. The zookeepers, meanwhile, are portrayed as dedicated individuals who care deeply for the animals, though they occasionally struggle with the demands of their work and the zoo's limited resources.

The plot is episodic, with each episode focusing on a specific event or challenge at the zoo. These range from preparing for a visitor's day and managing animal health issues to addressing conflicts between the animals or dealing with unexpected crises. The series balances comedic moments with heartfelt scenes, highlighting the bond between humans and animals and the importance of empathy and understanding in caring for wildlife.

Throughout the series, themes of cooperation, perseverance, and the value of life are explored. The animals and zookeepers often work together to overcome obstacles, demonstrating the importance of teamwork and mutual respect. The narrative also touches on broader issues such as conservation, animal welfare, and the ethical considerations of keeping animals in captivity, though these topics are presented in a way that is accessible and appropriate for a general audience.

The characters, both human and animal, are well-developed, with their interactions driving much of the story's charm. Kaba-Enchō, as the central figure, embodies a mix of authority and approachability, often mediating between the animals and the zookeepers. The series' tone remains consistently warm and engaging, making it an enjoyable watch for audiences of all ages.