"Leave it to PET!" is a science-fiction comedy manga centered around Noboru Yamada, a young boy who discovers a peculiar robot named PET (Perfect Electronic Transformer) in a junkyard. PET is no ordinary robot; it has the ability to transform into any object or machine, provided Noboru can draw a clear and accurate design of it. This unique ability becomes the foundation for the series' episodic adventures, as Noboru and PET navigate various challenges, often involving school life, bullies, and everyday problems.

The narrative primarily unfolds through self-contained chapters, each presenting a new scenario where PET's transformative abilities are put to the test. Noboru, though well-meaning, often struggles with his artistic skills, leading to humorous and sometimes disastrous outcomes when PET transforms based on imperfect designs. Despite these mishaps, PET remains loyal and resourceful, often saving the day in unexpected ways.

Supporting characters include Noboru's classmates and family, who occasionally become involved in PET's antics. Notable figures include Noboru's strict but caring mother, his mischievous younger sister, and his rival, a wealthy classmate who often tries to outdo Noboru with his own gadgets. The interactions between these characters add depth to the story, creating a blend of humor, light-hearted conflict, and occasional moments of heartfelt camaraderie.

The series balances its comedic tone with imaginative scenarios, showcasing PET's versatility and the creative potential of its premise. While the focus remains on humor and problem-solving, there are occasional hints of deeper themes, such as the value of friendship and the importance of perseverance. The episodic structure ensures that each chapter offers a fresh and engaging experience, making "Leave it to PET!" an accessible and entertaining read for a wide audience.